diff --git a/gstreamer/src/subclass/bin.rs b/gstreamer/src/subclass/bin.rs
index 51b51f309..19d1e4762 100644
--- a/gstreamer/src/subclass/bin.rs
+++ b/gstreamer/src/subclass/bin.rs
@@ -9,6 +9,7 @@
 use glib_sys;
 use gst_sys;
 
+use glib::prelude::*;
 use glib::translate::*;
 
 use super::prelude::*;
@@ -20,29 +21,33 @@ use LoggableError;
 use Message;
 
 pub trait BinImpl: BinImplExt + ElementImpl {
-    fn add_element(&self, bin: &Bin, element: &Element) -> Result<(), LoggableError> {
+    fn add_element(&self, bin: &Self::Type, element: &Element) -> Result<(), LoggableError> {
         self.parent_add_element(bin, element)
     }
 
-    fn remove_element(&self, bin: &Bin, element: &Element) -> Result<(), LoggableError> {
+    fn remove_element(&self, bin: &Self::Type, element: &Element) -> Result<(), LoggableError> {
         self.parent_remove_element(bin, element)
     }
 
-    fn handle_message(&self, bin: &Bin, message: Message) {
+    fn handle_message(&self, bin: &Self::Type, message: Message) {
         self.parent_handle_message(bin, message)
     }
 }
 
-pub trait BinImplExt {
-    fn parent_add_element(&self, bin: &Bin, element: &Element) -> Result<(), LoggableError>;
+pub trait BinImplExt: ObjectSubclass {
+    fn parent_add_element(&self, bin: &Self::Type, element: &Element) -> Result<(), LoggableError>;
 
-    fn parent_remove_element(&self, bin: &Bin, element: &Element) -> Result<(), LoggableError>;
+    fn parent_remove_element(
+        &self,
+        bin: &Self::Type,
+        element: &Element,
+    ) -> Result<(), LoggableError>;
 
-    fn parent_handle_message(&self, bin: &Bin, message: Message);
+    fn parent_handle_message(&self, bin: &Self::Type, message: Message);
 }
 
 impl<T: BinImpl> BinImplExt for T {
-    fn parent_add_element(&self, bin: &Bin, element: &Element) -> Result<(), LoggableError> {
+    fn parent_add_element(&self, bin: &Self::Type, element: &Element) -> Result<(), LoggableError> {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstBinClass;
@@ -50,14 +55,21 @@ impl<T: BinImpl> BinImplExt for T {
                 gst_loggable_error!(::CAT_RUST, "Parent function `add_element` is not defined")
             })?;
             gst_result_from_gboolean!(
-                f(bin.to_glib_none().0, element.to_glib_none().0),
+                f(
+                    bin.unsafe_cast_ref::<::Bin>().to_glib_none().0,
+                    element.to_glib_none().0
+                ),
                 ::CAT_RUST,
                 "Failed to add the element using the parent function"
             )
         }
     }
 
-    fn parent_remove_element(&self, bin: &Bin, element: &Element) -> Result<(), LoggableError> {
+    fn parent_remove_element(
+        &self,
+        bin: &Self::Type,
+        element: &Element,
+    ) -> Result<(), LoggableError> {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstBinClass;
@@ -68,19 +80,25 @@ impl<T: BinImpl> BinImplExt for T {
                 )
             })?;
             gst_result_from_gboolean!(
-                f(bin.to_glib_none().0, element.to_glib_none().0),
+                f(
+                    bin.unsafe_cast_ref::<::Bin>().to_glib_none().0,
+                    element.to_glib_none().0
+                ),
                 ::CAT_RUST,
                 "Failed to remove the element using the parent function"
             )
         }
     }
 
-    fn parent_handle_message(&self, bin: &Bin, message: Message) {
+    fn parent_handle_message(&self, bin: &Self::Type, message: Message) {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstBinClass;
             if let Some(ref f) = (*parent_class).handle_message {
-                f(bin.to_glib_none().0, message.into_ptr());
+                f(
+                    bin.unsafe_cast_ref::<::Bin>().to_glib_none().0,
+                    message.into_ptr(),
+                );
             }
         }
     }
@@ -111,7 +129,7 @@ where
     let wrap: Borrowed<Bin> = from_glib_borrow(ptr);
 
     gst_panic_to_error!(&wrap, &instance.panicked(), false, {
-        match imp.add_element(&wrap, &from_glib_none(element)) {
+        match imp.add_element(wrap.unsafe_cast_ref(), &from_glib_none(element)) {
             Ok(()) => true,
             Err(err) => {
                 err.log_with_object(&*wrap);
@@ -141,7 +159,7 @@ where
     }
 
     gst_panic_to_error!(&wrap, &instance.panicked(), false, {
-        match imp.remove_element(&wrap, &from_glib_none(element)) {
+        match imp.remove_element(wrap.unsafe_cast_ref(), &from_glib_none(element)) {
             Ok(()) => true,
             Err(err) => {
                 err.log_with_object(&*wrap);
@@ -163,6 +181,6 @@ unsafe extern "C" fn bin_handle_message<T: BinImpl>(
     let wrap: Borrowed<Bin> = from_glib_borrow(ptr);
 
     gst_panic_to_error!(&wrap, &instance.panicked(), (), {
-        imp.handle_message(&wrap, from_glib_full(message))
+        imp.handle_message(wrap.unsafe_cast_ref(), from_glib_full(message))
     });
 }
diff --git a/gstreamer/src/subclass/child_proxy.rs b/gstreamer/src/subclass/child_proxy.rs
index 853f5eab0..072fafa48 100644
--- a/gstreamer/src/subclass/child_proxy.rs
+++ b/gstreamer/src/subclass/child_proxy.rs
@@ -11,6 +11,7 @@ use gobject_sys;
 use gst_sys;
 
 use glib;
+use glib::prelude::*;
 use glib::subclass::prelude::*;
 use glib::translate::*;
 
@@ -19,7 +20,7 @@ use libc;
 use ChildProxy;
 
 pub trait ChildProxyImpl: ObjectImpl + Send + Sync {
-    fn get_child_by_name(&self, object: &ChildProxy, name: &str) -> Option<glib::Object> {
+    fn get_child_by_name(&self, object: &Self::Type, name: &str) -> Option<glib::Object> {
         unsafe {
             let type_ = gst_sys::gst_child_proxy_get_type();
             let iface = gobject_sys::g_type_default_interface_ref(type_)
@@ -27,7 +28,7 @@ pub trait ChildProxyImpl: ObjectImpl + Send + Sync {
             assert!(!iface.is_null());
 
             let ret = ((*iface).get_child_by_name.as_ref().unwrap())(
-                object.to_glib_none().0,
+                object.unsafe_cast_ref::<ChildProxy>().to_glib_none().0,
                 name.to_glib_none().0,
             );
 
@@ -37,11 +38,11 @@ pub trait ChildProxyImpl: ObjectImpl + Send + Sync {
         }
     }
 
-    fn get_child_by_index(&self, object: &ChildProxy, index: u32) -> Option<glib::Object>;
-    fn get_children_count(&self, object: &ChildProxy) -> u32;
+    fn get_child_by_index(&self, object: &Self::Type, index: u32) -> Option<glib::Object>;
+    fn get_children_count(&self, object: &Self::Type) -> u32;
 
-    fn child_added(&self, _object: &ChildProxy, _child: &glib::Object, _name: &str) {}
-    fn child_removed(&self, _object: &ChildProxy, _child: &glib::Object, _name: &str) {}
+    fn child_added(&self, _object: &Self::Type, _child: &glib::Object, _name: &str) {}
+    fn child_removed(&self, _object: &Self::Type, _child: &glib::Object, _name: &str) {}
 }
 
 unsafe impl<T: ChildProxyImpl> IsImplementable<T> for ChildProxy {
@@ -67,7 +68,7 @@ unsafe extern "C" fn child_proxy_get_child_by_name<T: ChildProxyImpl>(
     let imp = instance.get_impl();
 
     imp.get_child_by_name(
-        &from_glib_borrow(child_proxy),
+        &from_glib_borrow::<_, ChildProxy>(child_proxy).unsafe_cast_ref(),
         &glib::GString::from_glib_borrow(name),
     )
     .to_glib_full()
@@ -80,8 +81,11 @@ unsafe extern "C" fn child_proxy_get_child_by_index<T: ChildProxyImpl>(
     let instance = &*(child_proxy as *mut T::Instance);
     let imp = instance.get_impl();
 
-    imp.get_child_by_index(&from_glib_borrow(child_proxy), index)
-        .to_glib_full()
+    imp.get_child_by_index(
+        &from_glib_borrow::<_, ChildProxy>(child_proxy).unsafe_cast_ref(),
+        index,
+    )
+    .to_glib_full()
 }
 
 unsafe extern "C" fn child_proxy_get_children_count<T: ChildProxyImpl>(
@@ -90,7 +94,7 @@ unsafe extern "C" fn child_proxy_get_children_count<T: ChildProxyImpl>(
     let instance = &*(child_proxy as *mut T::Instance);
     let imp = instance.get_impl();
 
-    imp.get_children_count(&from_glib_borrow(child_proxy))
+    imp.get_children_count(&from_glib_borrow::<_, ChildProxy>(child_proxy).unsafe_cast_ref())
 }
 
 unsafe extern "C" fn child_proxy_child_added<T: ChildProxyImpl>(
@@ -102,7 +106,7 @@ unsafe extern "C" fn child_proxy_child_added<T: ChildProxyImpl>(
     let imp = instance.get_impl();
 
     imp.child_added(
-        &from_glib_borrow(child_proxy),
+        &from_glib_borrow::<_, ChildProxy>(child_proxy).unsafe_cast_ref(),
         &from_glib_borrow(child),
         &glib::GString::from_glib_borrow(name),
     )
@@ -117,7 +121,7 @@ unsafe extern "C" fn child_proxy_child_removed<T: ChildProxyImpl>(
     let imp = instance.get_impl();
 
     imp.child_removed(
-        &from_glib_borrow(child_proxy),
+        &from_glib_borrow::<_, ChildProxy>(child_proxy).unsafe_cast_ref(),
         &from_glib_borrow(child),
         &glib::GString::from_glib_borrow(name),
     )
diff --git a/gstreamer/src/subclass/clock.rs b/gstreamer/src/subclass/clock.rs
index 96133252b..cb01d1abc 100644
--- a/gstreamer/src/subclass/clock.rs
+++ b/gstreamer/src/subclass/clock.rs
@@ -24,59 +24,63 @@ use ClockTimeDiff;
 pub trait ClockImpl: ClockImplExt + ObjectImpl + Send + Sync {
     fn change_resolution(
         &self,
-        clock: &Clock,
+        clock: &Self::Type,
         old_resolution: ClockTime,
         new_resolution: ClockTime,
     ) -> ClockTime {
         self.parent_change_resolution(clock, old_resolution, new_resolution)
     }
 
-    fn get_resolution(&self, clock: &Clock) -> ClockTime {
+    fn get_resolution(&self, clock: &Self::Type) -> ClockTime {
         self.parent_get_resolution(clock)
     }
 
-    fn get_internal_time(&self, clock: &Clock) -> ClockTime {
+    fn get_internal_time(&self, clock: &Self::Type) -> ClockTime {
         self.parent_get_internal_time(clock)
     }
 
     fn wait(
         &self,
-        clock: &Clock,
+        clock: &Self::Type,
         id: &ClockId,
     ) -> (Result<ClockSuccess, ClockError>, ClockTimeDiff) {
         self.parent_wait(clock, id)
     }
 
-    fn wait_async(&self, clock: &Clock, id: &ClockId) -> Result<ClockSuccess, ClockError> {
+    fn wait_async(&self, clock: &Self::Type, id: &ClockId) -> Result<ClockSuccess, ClockError> {
         self.parent_wait_async(clock, id)
     }
 
-    fn unschedule(&self, clock: &Clock, id: &ClockId) {
+    fn unschedule(&self, clock: &Self::Type, id: &ClockId) {
         self.parent_unschedule(clock, id)
     }
 }
 
-pub trait ClockImplExt {
+pub trait ClockImplExt: ObjectSubclass {
     fn parent_change_resolution(
         &self,
-        clock: &Clock,
+        clock: &Self::Type,
         old_resolution: ClockTime,
         new_resolution: ClockTime,
     ) -> ClockTime;
 
-    fn parent_get_resolution(&self, clock: &Clock) -> ClockTime;
+    fn parent_get_resolution(&self, clock: &Self::Type) -> ClockTime;
 
-    fn parent_get_internal_time(&self, clock: &Clock) -> ClockTime;
+    fn parent_get_internal_time(&self, clock: &Self::Type) -> ClockTime;
 
     fn parent_wait(
         &self,
-        clock: &Clock,
+        clock: &Self::Type,
         id: &ClockId,
     ) -> (Result<ClockSuccess, ClockError>, ClockTimeDiff);
 
-    fn parent_wait_async(&self, clock: &Clock, id: &ClockId) -> Result<ClockSuccess, ClockError>;
+    fn parent_wait_async(
+        &self,
+        clock: &Self::Type,
+        id: &ClockId,
+    ) -> Result<ClockSuccess, ClockError>;
 
-    fn parent_unschedule(&self, clock: &Clock, id: &ClockId);
+    fn parent_unschedule(&self, clock: &Self::Type, id: &ClockId);
 
     fn wake_id(&self, id: &ClockId)
     where
@@ -87,7 +91,7 @@ pub trait ClockImplExt {
 impl<T: ClockImpl> ClockImplExt for T {
     fn parent_change_resolution(
         &self,
-        clock: &Clock,
+        clock: &Self::Type,
         old_resolution: ClockTime,
         new_resolution: ClockTime,
     ) -> ClockTime {
@@ -97,7 +101,7 @@ impl<T: ClockImpl> ClockImplExt for T {
 
             if let Some(func) = (*parent_class).change_resolution {
                 from_glib(func(
-                    clock.to_glib_none().0,
+                    clock.unsafe_cast_ref::<Clock>().to_glib_none().0,
                     old_resolution.to_glib(),
                     new_resolution.to_glib(),
                 ))
@@ -107,7 +111,7 @@ impl<T: ClockImpl> ClockImplExt for T {
         }
     }
 
-    fn parent_get_resolution(&self, clock: &Clock) -> ClockTime {
+    fn parent_get_resolution(&self, clock: &Self::Type) -> ClockTime {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstClockClass;
@@ -115,13 +119,13 @@ impl<T: ClockImpl> ClockImplExt for T {
             from_glib(
                 (*parent_class)
                     .get_resolution
-                    .map(|f| f(clock.to_glib_none().0))
+                    .map(|f| f(clock.unsafe_cast_ref::<Clock>().to_glib_none().0))
                     .unwrap_or(1),
             )
         }
     }
 
-    fn parent_get_internal_time(&self, clock: &Clock) -> ClockTime {
+    fn parent_get_internal_time(&self, clock: &Self::Type) -> ClockTime {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstClockClass;
@@ -129,7 +133,7 @@ impl<T: ClockImpl> ClockImplExt for T {
             from_glib(
                 (*parent_class)
                     .get_internal_time
-                    .map(|f| f(clock.to_glib_none().0))
+                    .map(|f| f(clock.unsafe_cast_ref::<Clock>().to_glib_none().0))
                     .unwrap_or(0),
             )
         }
@@ -137,7 +141,7 @@ impl<T: ClockImpl> ClockImplExt for T {
 
     fn parent_wait(
         &self,
-        clock: &Clock,
+        clock: &Self::Type,
         id: &ClockId,
     ) -> (Result<ClockSuccess, ClockError>, ClockTimeDiff) {
         unsafe {
@@ -151,7 +155,7 @@ impl<T: ClockImpl> ClockImplExt for T {
                         .wait
                         .map(|f| {
                             f(
-                                clock.to_glib_none().0,
+                                clock.unsafe_cast_ref::<Clock>().to_glib_none().0,
                                 id.to_glib_none().0 as *mut gst_sys::GstClockEntry,
                                 &mut jitter,
                             )
@@ -164,7 +168,11 @@ impl<T: ClockImpl> ClockImplExt for T {
         }
     }
 
-    fn parent_wait_async(&self, clock: &Clock, id: &ClockId) -> Result<ClockSuccess, ClockError> {
+    fn parent_wait_async(
+        &self,
+        clock: &Self::Type,
+        id: &ClockId,
+    ) -> Result<ClockSuccess, ClockError> {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstClockClass;
@@ -173,7 +181,7 @@ impl<T: ClockImpl> ClockImplExt for T {
                     .wait_async
                     .map(|f| {
                         f(
-                            clock.to_glib_none().0,
+                            clock.unsafe_cast_ref::<Clock>().to_glib_none().0,
                             id.to_glib_none().0 as *mut gst_sys::GstClockEntry,
                         )
                     })
@@ -183,13 +191,13 @@ impl<T: ClockImpl> ClockImplExt for T {
         }
     }
 
-    fn parent_unschedule(&self, clock: &Clock, id: &ClockId) {
+    fn parent_unschedule(&self, clock: &Self::Type, id: &ClockId) {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstClockClass;
             if let Some(func) = (*parent_class).unschedule {
                 func(
-                    clock.to_glib_none().0,
+                    clock.unsafe_cast_ref::<Clock>().to_glib_none().0,
                     id.to_glib_none().0 as *mut gst_sys::GstClockEntry,
                 );
             }
@@ -254,8 +262,12 @@ unsafe extern "C" fn clock_change_resolution<T: ClockImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<Clock> = from_glib_borrow(ptr);
 
-    imp.change_resolution(&wrap, from_glib(old_resolution), from_glib(new_resolution))
-        .to_glib()
+    imp.change_resolution(
+        wrap.unsafe_cast_ref(),
+        from_glib(old_resolution),
+        from_glib(new_resolution),
+    )
+    .to_glib()
 }
 
 unsafe extern "C" fn clock_get_resolution<T: ClockImpl>(
@@ -265,7 +277,7 @@ unsafe extern "C" fn clock_get_resolution<T: ClockImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<Clock> = from_glib_borrow(ptr);
 
-    imp.get_resolution(&wrap).to_glib()
+    imp.get_resolution(wrap.unsafe_cast_ref()).to_glib()
 }
 
 unsafe extern "C" fn clock_get_internal_time<T: ClockImpl>(
@@ -275,7 +287,7 @@ unsafe extern "C" fn clock_get_internal_time<T: ClockImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<Clock> = from_glib_borrow(ptr);
 
-    imp.get_internal_time(&wrap).to_glib()
+    imp.get_internal_time(wrap.unsafe_cast_ref()).to_glib()
 }
 
 unsafe extern "C" fn clock_wait<T: ClockImpl>(
@@ -287,7 +299,10 @@ unsafe extern "C" fn clock_wait<T: ClockImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<Clock> = from_glib_borrow(ptr);
 
-    let (res, j) = imp.wait(&wrap, &from_glib_borrow(id as gst_sys::GstClockID));
+    let (res, j) = imp.wait(
+        wrap.unsafe_cast_ref(),
+        &from_glib_borrow(id as gst_sys::GstClockID),
+    );
     if !jitter.is_null() {
         *jitter = j;
     }
@@ -303,7 +318,11 @@ unsafe extern "C" fn clock_wait_async<T: ClockImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<Clock> = from_glib_borrow(ptr);
 
-    ClockReturn::from(imp.wait_async(&wrap, &from_glib_borrow(id as gst_sys::GstClockID))).to_glib()
+    ClockReturn::from(imp.wait_async(
+        wrap.unsafe_cast_ref(),
+        &from_glib_borrow(id as gst_sys::GstClockID),
+    ))
+    .to_glib()
 }
 
 unsafe extern "C" fn clock_unschedule<T: ClockImpl>(
@@ -314,5 +333,8 @@ unsafe extern "C" fn clock_unschedule<T: ClockImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<Clock> = from_glib_borrow(ptr);
 
-    imp.unschedule(&wrap, &from_glib_borrow(id as gst_sys::GstClockID));
+    imp.unschedule(
+        wrap.unsafe_cast_ref(),
+        &from_glib_borrow(id as gst_sys::GstClockID),
+    );
 }
diff --git a/gstreamer/src/subclass/device.rs b/gstreamer/src/subclass/device.rs
index 383dac0b8..25ba9c599 100644
--- a/gstreamer/src/subclass/device.rs
+++ b/gstreamer/src/subclass/device.rs
@@ -9,9 +9,9 @@
 use glib_sys;
 use gst_sys;
 
-use glib::translate::*;
-
+use glib::prelude::*;
 use glib::subclass::prelude::*;
+use glib::translate::*;
 
 use Device;
 use Element;
@@ -22,27 +22,31 @@ use std::ptr;
 pub trait DeviceImpl: DeviceImplExt + ObjectImpl + Send + Sync {
     fn create_element(
         &self,
-        device: &Device,
+        device: &Self::Type,
         name: Option<&str>,
     ) -> Result<Element, LoggableError> {
         self.parent_create_element(device, name)
     }
 
-    fn reconfigure_element(&self, device: &Device, element: &Element) -> Result<(), LoggableError> {
+    fn reconfigure_element(
+        &self,
+        device: &Self::Type,
+        element: &Element,
+    ) -> Result<(), LoggableError> {
         self.parent_reconfigure_element(device, element)
     }
 }
 
-pub trait DeviceImplExt {
+pub trait DeviceImplExt: ObjectSubclass {
     fn parent_create_element(
         &self,
-        device: &Device,
+        device: &Self::Type,
         name: Option<&str>,
     ) -> Result<Element, LoggableError>;
 
     fn parent_reconfigure_element(
         &self,
-        device: &Device,
+        device: &Self::Type,
         element: &Element,
     ) -> Result<(), LoggableError>;
 }
@@ -50,14 +54,17 @@ pub trait DeviceImplExt {
 impl<T: DeviceImpl> DeviceImplExt for T {
     fn parent_create_element(
         &self,
-        device: &Device,
+        device: &Self::Type,
         name: Option<&str>,
     ) -> Result<Element, LoggableError> {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstDeviceClass;
             if let Some(f) = (*parent_class).create_element {
-                let ptr = f(device.to_glib_none().0, name.to_glib_none().0);
+                let ptr = f(
+                    device.unsafe_cast_ref::<Device>().to_glib_none().0,
+                    name.to_glib_none().0,
+                );
 
                 // Don't steal floating reference here but pass it further to the caller
                 Option::<_>::from_glib_full(ptr).ok_or_else(|| {
@@ -77,7 +84,7 @@ impl<T: DeviceImpl> DeviceImplExt for T {
 
     fn parent_reconfigure_element(
         &self,
-        device: &Device,
+        device: &Self::Type,
         element: &Element,
     ) -> Result<(), LoggableError> {
         unsafe {
@@ -90,7 +97,10 @@ impl<T: DeviceImpl> DeviceImplExt for T {
                 )
             })?;
             gst_result_from_gboolean!(
-                f(device.to_glib_none().0, element.to_glib_none().0),
+                f(
+                    device.unsafe_cast_ref::<Device>().to_glib_none().0,
+                    element.to_glib_none().0
+                ),
                 ::CAT_RUST,
                 "Failed to reconfigure the element using the parent function"
             )
@@ -116,7 +126,7 @@ unsafe extern "C" fn device_create_element<T: DeviceImpl>(
     let wrap: Borrowed<Device> = from_glib_borrow(ptr);
 
     match imp.create_element(
-        &wrap,
+        wrap.unsafe_cast_ref(),
         Option::<glib::GString>::from_glib_borrow(name)
             .as_ref()
             .as_ref()
@@ -146,7 +156,7 @@ unsafe extern "C" fn device_reconfigure_element<T: DeviceImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<Device> = from_glib_borrow(ptr);
 
-    match imp.reconfigure_element(&wrap, &from_glib_borrow(element)) {
+    match imp.reconfigure_element(wrap.unsafe_cast_ref(), &from_glib_borrow(element)) {
         Ok(()) => true,
         Err(err) => {
             err.log_with_object(&*wrap);
diff --git a/gstreamer/src/subclass/device_provider.rs b/gstreamer/src/subclass/device_provider.rs
index 111193483..9b2e86584 100644
--- a/gstreamer/src/subclass/device_provider.rs
+++ b/gstreamer/src/subclass/device_provider.rs
@@ -9,51 +9,54 @@
 use glib_sys;
 use gst_sys;
 
-use glib::translate::*;
-
+use glib::prelude::*;
 use glib::subclass::prelude::*;
+use glib::translate::*;
 
 use Device;
 use DeviceProvider;
 use LoggableError;
 
 pub trait DeviceProviderImpl: DeviceProviderImplExt + ObjectImpl + Send + Sync {
-    fn probe(&self, device_provider: &DeviceProvider) -> Vec<Device> {
+    fn probe(&self, device_provider: &Self::Type) -> Vec<Device> {
         self.parent_probe(device_provider)
     }
 
-    fn start(&self, device_provider: &DeviceProvider) -> Result<(), LoggableError> {
+    fn start(&self, device_provider: &Self::Type) -> Result<(), LoggableError> {
         self.parent_start(device_provider)
     }
 
-    fn stop(&self, device_provider: &DeviceProvider) {
+    fn stop(&self, device_provider: &Self::Type) {
         self.parent_stop(device_provider)
     }
 }
 
-pub trait DeviceProviderImplExt {
-    fn parent_probe(&self, device_provider: &DeviceProvider) -> Vec<Device>;
+pub trait DeviceProviderImplExt: ObjectSubclass {
+    fn parent_probe(&self, device_provider: &Self::Type) -> Vec<Device>;
 
-    fn parent_start(&self, device_provider: &DeviceProvider) -> Result<(), LoggableError>;
+    fn parent_start(&self, device_provider: &Self::Type) -> Result<(), LoggableError>;
 
-    fn parent_stop(&self, device_provider: &DeviceProvider);
+    fn parent_stop(&self, device_provider: &Self::Type);
 }
 
 impl<T: DeviceProviderImpl> DeviceProviderImplExt for T {
-    fn parent_probe(&self, device_provider: &DeviceProvider) -> Vec<Device> {
+    fn parent_probe(&self, device_provider: &Self::Type) -> Vec<Device> {
         unsafe {
             let data = T::type_data();
             let parent_class =
                 data.as_ref().get_parent_class() as *mut gst_sys::GstDeviceProviderClass;
             if let Some(f) = (*parent_class).probe {
-                FromGlibPtrContainer::from_glib_full(f(device_provider.to_glib_none().0))
+                FromGlibPtrContainer::from_glib_full(f(device_provider
+                    .unsafe_cast_ref::<DeviceProvider>()
+                    .to_glib_none()
+                    .0))
             } else {
                 Vec::new()
             }
         }
     }
 
-    fn parent_start(&self, device_provider: &DeviceProvider) -> Result<(), LoggableError> {
+    fn parent_start(&self, device_provider: &Self::Type) -> Result<(), LoggableError> {
         unsafe {
             let data = T::type_data();
             let parent_class =
@@ -62,20 +65,26 @@ impl<T: DeviceProviderImpl> DeviceProviderImplExt for T {
                 gst_loggable_error!(::CAT_RUST, "Parent function `start` is not defined")
             })?;
             gst_result_from_gboolean!(
-                f(device_provider.to_glib_none().0),
+                f(device_provider
+                    .unsafe_cast_ref::<DeviceProvider>()
+                    .to_glib_none()
+                    .0),
                 ::CAT_RUST,
                 "Failed to start the device provider using the parent function"
             )
         }
     }
 
-    fn parent_stop(&self, device_provider: &DeviceProvider) {
+    fn parent_stop(&self, device_provider: &Self::Type) {
         unsafe {
             let data = T::type_data();
             let parent_class =
                 data.as_ref().get_parent_class() as *mut gst_sys::GstDeviceProviderClass;
             if let Some(f) = (*parent_class).stop {
-                f(device_provider.to_glib_none().0);
+                f(device_provider
+                    .unsafe_cast_ref::<DeviceProvider>()
+                    .to_glib_none()
+                    .0);
             }
         }
     }
@@ -130,7 +139,7 @@ unsafe extern "C" fn device_provider_probe<T: DeviceProviderImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<DeviceProvider> = from_glib_borrow(ptr);
 
-    imp.probe(&wrap).to_glib_full()
+    imp.probe(wrap.unsafe_cast_ref()).to_glib_full()
 }
 
 unsafe extern "C" fn device_provider_start<T: DeviceProviderImpl>(
@@ -140,7 +149,7 @@ unsafe extern "C" fn device_provider_start<T: DeviceProviderImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<DeviceProvider> = from_glib_borrow(ptr);
 
-    match imp.start(&wrap) {
+    match imp.start(wrap.unsafe_cast_ref()) {
         Ok(()) => true,
         Err(err) => {
             err.log_with_object(&*wrap);
@@ -157,5 +166,5 @@ unsafe extern "C" fn device_provider_stop<T: DeviceProviderImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<DeviceProvider> = from_glib_borrow(ptr);
 
-    imp.stop(&wrap);
+    imp.stop(wrap.unsafe_cast_ref());
 }
diff --git a/gstreamer/src/subclass/element.rs b/gstreamer/src/subclass/element.rs
index df2997cc7..5ce19b3fb 100644
--- a/gstreamer/src/subclass/element.rs
+++ b/gstreamer/src/subclass/element.rs
@@ -30,7 +30,7 @@ use StateChangeSuccess;
 pub trait ElementImpl: ElementImplExt + ObjectImpl + Send + Sync {
     fn change_state(
         &self,
-        element: &::Element,
+        element: &Self::Type,
         transition: StateChange,
     ) -> Result<StateChangeSuccess, StateChangeError> {
         self.parent_change_state(element, transition)
@@ -38,7 +38,7 @@ pub trait ElementImpl: ElementImplExt + ObjectImpl + Send + Sync {
 
     fn request_new_pad(
         &self,
-        element: &::Element,
+        element: &Self::Type,
         templ: &::PadTemplate,
         name: Option<String>,
         caps: Option<&::Caps>,
@@ -46,77 +46,72 @@ pub trait ElementImpl: ElementImplExt + ObjectImpl + Send + Sync {
         self.parent_request_new_pad(element, templ, name, caps)
     }
 
-    fn release_pad(&self, element: &::Element, pad: &::Pad) {
+    fn release_pad(&self, element: &Self::Type, pad: &::Pad) {
         self.parent_release_pad(element, pad)
     }
 
-    fn send_event(&self, element: &::Element, event: Event) -> bool {
+    fn send_event(&self, element: &Self::Type, event: Event) -> bool {
         self.parent_send_event(element, event)
     }
 
-    fn query(&self, element: &::Element, query: &mut QueryRef) -> bool {
+    fn query(&self, element: &Self::Type, query: &mut QueryRef) -> bool {
         self.parent_query(element, query)
     }
 
-    fn set_context(&self, element: &::Element, context: &::Context) {
+    fn set_context(&self, element: &Self::Type, context: &::Context) {
         self.parent_set_context(element, context)
     }
 
-    fn set_clock(&self, element: &::Element, clock: Option<&::Clock>) -> bool {
+    fn set_clock(&self, element: &Self::Type, clock: Option<&::Clock>) -> bool {
         self.parent_set_clock(element, clock)
     }
 
-    fn provide_clock(&self, element: &::Element) -> Option<::Clock> {
+    fn provide_clock(&self, element: &Self::Type) -> Option<::Clock> {
         self.parent_provide_clock(element)
     }
 
-    fn post_message(&self, element: &::Element, msg: ::Message) -> bool {
+    fn post_message(&self, element: &Self::Type, msg: ::Message) -> bool {
         self.parent_post_message(element, msg)
     }
 }
 
-pub trait ElementImplExt {
+pub trait ElementImplExt: ObjectSubclass {
     fn parent_change_state(
         &self,
-        element: &::Element,
+        element: &Self::Type,
         transition: StateChange,
     ) -> Result<StateChangeSuccess, StateChangeError>;
 
     fn parent_request_new_pad(
         &self,
-        element: &::Element,
+        element: &Self::Type,
         templ: &::PadTemplate,
         name: Option<String>,
         caps: Option<&::Caps>,
     ) -> Option<::Pad>;
 
-    fn parent_release_pad(&self, element: &::Element, pad: &::Pad);
+    fn parent_release_pad(&self, element: &Self::Type, pad: &::Pad);
 
-    fn parent_send_event(&self, element: &::Element, event: Event) -> bool;
+    fn parent_send_event(&self, element: &Self::Type, event: Event) -> bool;
 
-    fn parent_query(&self, element: &::Element, query: &mut QueryRef) -> bool;
+    fn parent_query(&self, element: &Self::Type, query: &mut QueryRef) -> bool;
 
-    fn parent_set_context(&self, element: &::Element, context: &::Context);
+    fn parent_set_context(&self, element: &Self::Type, context: &::Context);
 
-    fn parent_set_clock(&self, element: &::Element, clock: Option<&::Clock>) -> bool;
+    fn parent_set_clock(&self, element: &Self::Type, clock: Option<&::Clock>) -> bool;
 
-    fn parent_provide_clock(&self, element: &::Element) -> Option<::Clock>;
+    fn parent_provide_clock(&self, element: &Self::Type) -> Option<::Clock>;
 
-    fn parent_post_message(&self, element: &::Element, msg: ::Message) -> bool;
+    fn parent_post_message(&self, element: &Self::Type, msg: ::Message) -> bool;
 
-    fn catch_panic<
-        R,
-        F: FnOnce(&Self) -> R,
-        G: FnOnce() -> R,
-        P: IsA<::Element> + IsA<glib::Object> + glib::value::SetValue,
-    >(
+    fn catch_panic<R, F: FnOnce(&Self) -> R, G: FnOnce() -> R, P: IsA<Element>>(
         &self,
         element: &P,
         fallback: G,
         f: F,
     ) -> R;
 
-    fn catch_panic_pad_function<R, F: FnOnce(&Self, &::Element) -> R, G: FnOnce() -> R>(
+    fn catch_panic_pad_function<R, F: FnOnce(&Self, &Self::Type) -> R, G: FnOnce() -> R>(
         parent: Option<&::Object>,
         fallback: G,
         f: F,
@@ -129,7 +124,7 @@ where
 {
     fn parent_change_state(
         &self,
-        element: &::Element,
+        element: &Self::Type,
         transition: StateChange,
     ) -> Result<StateChangeSuccess, StateChangeError> {
         unsafe {
@@ -139,14 +134,17 @@ where
             let f = (*parent_class)
                 .change_state
                 .expect("Missing parent function `change_state`");
-            StateChangeReturn::from_glib(f(element.to_glib_none().0, transition.to_glib()))
-                .into_result()
+            StateChangeReturn::from_glib(f(
+                element.unsafe_cast_ref::<Element>().to_glib_none().0,
+                transition.to_glib(),
+            ))
+            .into_result()
         }
     }
 
     fn parent_request_new_pad(
         &self,
-        element: &::Element,
+        element: &Self::Type,
         templ: &::PadTemplate,
         name: Option<String>,
         caps: Option<&::Caps>,
@@ -159,7 +157,7 @@ where
                 .request_new_pad
                 .map(|f| {
                     from_glib_none(f(
-                        element.to_glib_none().0,
+                        element.unsafe_cast_ref::<Element>().to_glib_none().0,
                         templ.to_glib_none().0,
                         name.to_glib_full(),
                         caps.to_glib_none().0,
@@ -169,97 +167,120 @@ where
         }
     }
 
-    fn parent_release_pad(&self, element: &::Element, pad: &::Pad) {
+    fn parent_release_pad(&self, element: &Self::Type, pad: &::Pad) {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstElementClass;
 
             (*parent_class)
                 .release_pad
-                .map(|f| f(element.to_glib_none().0, pad.to_glib_none().0))
+                .map(|f| {
+                    f(
+                        element.unsafe_cast_ref::<Element>().to_glib_none().0,
+                        pad.to_glib_none().0,
+                    )
+                })
                 .unwrap_or(())
         }
     }
 
-    fn parent_send_event(&self, element: &::Element, event: Event) -> bool {
+    fn parent_send_event(&self, element: &Self::Type, event: Event) -> bool {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstElementClass;
 
             (*parent_class)
                 .send_event
-                .map(|f| from_glib(f(element.to_glib_none().0, event.into_ptr())))
+                .map(|f| {
+                    from_glib(f(
+                        element.unsafe_cast_ref::<Element>().to_glib_none().0,
+                        event.into_ptr(),
+                    ))
+                })
                 .unwrap_or(false)
         }
     }
 
-    fn parent_query(&self, element: &::Element, query: &mut QueryRef) -> bool {
+    fn parent_query(&self, element: &Self::Type, query: &mut QueryRef) -> bool {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstElementClass;
 
             (*parent_class)
                 .query
-                .map(|f| from_glib(f(element.to_glib_none().0, query.as_mut_ptr())))
+                .map(|f| {
+                    from_glib(f(
+                        element.unsafe_cast_ref::<Element>().to_glib_none().0,
+                        query.as_mut_ptr(),
+                    ))
+                })
                 .unwrap_or(false)
         }
     }
 
-    fn parent_set_context(&self, element: &::Element, context: &::Context) {
+    fn parent_set_context(&self, element: &Self::Type, context: &::Context) {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstElementClass;
 
             (*parent_class)
                 .set_context
-                .map(|f| f(element.to_glib_none().0, context.to_glib_none().0))
+                .map(|f| {
+                    f(
+                        element.unsafe_cast_ref::<Element>().to_glib_none().0,
+                        context.to_glib_none().0,
+                    )
+                })
                 .unwrap_or(())
         }
     }
 
-    fn parent_set_clock(&self, element: &::Element, clock: Option<&::Clock>) -> bool {
+    fn parent_set_clock(&self, element: &Self::Type, clock: Option<&::Clock>) -> bool {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstElementClass;
 
             (*parent_class)
                 .set_clock
-                .map(|f| from_glib(f(element.to_glib_none().0, clock.to_glib_none().0)))
+                .map(|f| {
+                    from_glib(f(
+                        element.unsafe_cast_ref::<Element>().to_glib_none().0,
+                        clock.to_glib_none().0,
+                    ))
+                })
                 .unwrap_or(false)
         }
     }
 
-    fn parent_provide_clock(&self, element: &::Element) -> Option<::Clock> {
+    fn parent_provide_clock(&self, element: &Self::Type) -> Option<::Clock> {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstElementClass;
 
             (*parent_class)
                 .provide_clock
-                .map(|f| from_glib_none(f(element.to_glib_none().0)))
+                .map(|f| from_glib_none(f(element.unsafe_cast_ref::<Element>().to_glib_none().0)))
                 .unwrap_or(None)
         }
     }
 
-    fn parent_post_message(&self, element: &::Element, msg: ::Message) -> bool {
+    fn parent_post_message(&self, element: &Self::Type, msg: ::Message) -> bool {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstElementClass;
 
             if let Some(f) = (*parent_class).post_message {
-                from_glib(f(element.to_glib_none().0, msg.into_ptr()))
+                from_glib(f(
+                    element.unsafe_cast_ref::<Element>().to_glib_none().0,
+                    msg.into_ptr(),
+                ))
             } else {
                 false
             }
         }
     }
 
-    fn catch_panic<
-        R,
-        F: FnOnce(&Self) -> R,
-        G: FnOnce() -> R,
-        P: IsA<::Element> + IsA<glib::Object> + glib::value::SetValue,
-    >(
+    fn catch_panic<R, F: FnOnce(&Self) -> R, G: FnOnce() -> R, P: IsA<Element>>(
         &self,
         element: &P,
         fallback: G,
@@ -275,23 +296,21 @@ where
         }
     }
 
-    fn catch_panic_pad_function<R, F: FnOnce(&Self, &::Element) -> R, G: FnOnce() -> R>(
+    fn catch_panic_pad_function<R, F: FnOnce(&Self, &Self::Type) -> R, G: FnOnce() -> R>(
         parent: Option<&::Object>,
         fallback: G,
         f: F,
     ) -> R {
         unsafe {
-            let wrap = parent
-                .as_ref()
-                .unwrap()
-                .downcast_ref::<::Element>()
-                .unwrap();
+            let wrap = parent.as_ref().unwrap().downcast_ref::<Element>().unwrap();
             assert!(wrap.get_type().is_a(&T::get_type()));
             let ptr: *mut gst_sys::GstElement = wrap.to_glib_none().0;
             let instance = &*(ptr as *mut T::Instance);
             let imp = instance.get_impl();
 
-            gst_panic_to_error!(wrap, &instance.panicked(), fallback(), { f(&imp, &wrap) })
+            gst_panic_to_error!(wrap, &instance.panicked(), fallback(), {
+                f(&imp, wrap.unsafe_cast_ref())
+            })
         }
     }
 }
@@ -378,7 +397,7 @@ where
     };
 
     gst_panic_to_error!(&wrap, &instance.panicked(), fallback, {
-        imp.change_state(&wrap, transition).into()
+        imp.change_state(wrap.unsafe_cast_ref(), transition).into()
     })
     .to_glib()
 }
@@ -402,7 +421,7 @@ where
     // See https://bugzilla.gnome.org/show_bug.cgi?id=791193
     let pad = gst_panic_to_error!(&wrap, &instance.panicked(), None, {
         imp.request_new_pad(
-            &wrap,
+            wrap.unsafe_cast_ref(),
             &from_glib_borrow(templ),
             from_glib_none(name),
             caps.as_ref().as_ref(),
@@ -437,7 +456,7 @@ unsafe extern "C" fn element_release_pad<T: ElementImpl>(
     }
 
     gst_panic_to_error!(&wrap, &instance.panicked(), (), {
-        imp.release_pad(&wrap, &from_glib_none(pad))
+        imp.release_pad(wrap.unsafe_cast_ref(), &from_glib_none(pad))
     })
 }
 
@@ -453,7 +472,7 @@ where
     let wrap: Borrowed<Element> = from_glib_borrow(ptr);
 
     gst_panic_to_error!(&wrap, &instance.panicked(), false, {
-        imp.send_event(&wrap, from_glib_full(event))
+        imp.send_event(wrap.unsafe_cast_ref(), from_glib_full(event))
     })
     .to_glib()
 }
@@ -471,7 +490,7 @@ where
     let query = QueryRef::from_mut_ptr(query);
 
     gst_panic_to_error!(&wrap, &instance.panicked(), false, {
-        imp.query(&wrap, query)
+        imp.query(wrap.unsafe_cast_ref(), query)
     })
     .to_glib()
 }
@@ -487,7 +506,7 @@ unsafe extern "C" fn element_set_context<T: ElementImpl>(
     let wrap: Borrowed<Element> = from_glib_borrow(ptr);
 
     gst_panic_to_error!(&wrap, &instance.panicked(), (), {
-        imp.set_context(&wrap, &from_glib_borrow(context))
+        imp.set_context(wrap.unsafe_cast_ref(), &from_glib_borrow(context))
     })
 }
 
@@ -505,7 +524,7 @@ where
     let clock = Option::<::Clock>::from_glib_borrow(clock);
 
     gst_panic_to_error!(&wrap, &instance.panicked(), false, {
-        imp.set_clock(&wrap, clock.as_ref().as_ref())
+        imp.set_clock(wrap.unsafe_cast_ref(), clock.as_ref().as_ref())
     })
     .to_glib()
 }
@@ -521,7 +540,7 @@ where
     let wrap: Borrowed<Element> = from_glib_borrow(ptr);
 
     gst_panic_to_error!(&wrap, &instance.panicked(), None, {
-        imp.provide_clock(&wrap)
+        imp.provide_clock(wrap.unsafe_cast_ref())
     })
     .to_glib_full()
 }
@@ -539,7 +558,8 @@ where
 
     // Can't catch panics here as posting the error message would cause
     // this code to be called again recursively forever.
-    imp.post_message(&wrap, from_glib_full(msg)).to_glib()
+    imp.post_message(wrap.unsafe_cast_ref(), from_glib_full(msg))
+        .to_glib()
 }
 
 #[cfg(test)]
@@ -549,6 +569,8 @@ mod tests {
     use glib::subclass;
     use std::sync::atomic;
 
+    use ElementFactory;
+
     pub mod imp {
         use super::*;
 
@@ -563,34 +585,44 @@ mod tests {
             fn sink_chain(
                 &self,
                 _pad: &::Pad,
-                _element: &::Element,
+                _element: &super::TestElement,
                 buffer: ::Buffer,
             ) -> Result<::FlowSuccess, ::FlowError> {
                 self.n_buffers.fetch_add(1, atomic::Ordering::SeqCst);
                 self.srcpad.push(buffer)
             }
 
-            fn sink_event(&self, _pad: &::Pad, _element: &::Element, event: ::Event) -> bool {
+            fn sink_event(
+                &self,
+                _pad: &::Pad,
+                _element: &super::TestElement,
+                event: ::Event,
+            ) -> bool {
                 self.srcpad.push_event(event)
             }
 
             fn sink_query(
                 &self,
                 _pad: &::Pad,
-                _element: &::Element,
+                _element: &super::TestElement,
                 query: &mut ::QueryRef,
             ) -> bool {
                 self.srcpad.peer_query(query)
             }
 
-            fn src_event(&self, _pad: &::Pad, _element: &::Element, event: ::Event) -> bool {
+            fn src_event(
+                &self,
+                _pad: &::Pad,
+                _element: &super::TestElement,
+                event: ::Event,
+            ) -> bool {
                 self.sinkpad.push_event(event)
             }
 
             fn src_query(
                 &self,
                 _pad: &::Pad,
-                _element: &::Element,
+                _element: &super::TestElement,
                 query: &mut ::QueryRef,
             ) -> bool {
                 self.sinkpad.peer_query(query)
@@ -600,13 +632,13 @@ mod tests {
         impl ObjectSubclass for TestElement {
             const NAME: &'static str = "TestElement";
             type Type = super::TestElement;
-            type ParentType = ::Element;
+            type ParentType = Element;
             type Instance = ::subclass::ElementInstanceStruct<Self>;
             type Class = subclass::simple::ClassStruct<Self>;
 
             glib_object_subclass!();
 
-            fn with_class(klass: &subclass::simple::ClassStruct<Self>) -> Self {
+            fn with_class(klass: &Self::Class) -> Self {
                 let templ = klass.get_pad_template("sink").unwrap();
                 let sinkpad = ::Pad::builder_with_template(&templ, Some("sink"))
                     .chain_function(|pad, parent, buffer| {
@@ -658,7 +690,7 @@ mod tests {
                 }
             }
 
-            fn class_init(klass: &mut subclass::simple::ClassStruct<Self>) {
+            fn class_init(klass: &mut Self::Class) {
                 klass.set_metadata(
                     "Test Element",
                     "Generic",
@@ -691,7 +723,7 @@ mod tests {
         impl ElementImpl for TestElement {
             fn change_state(
                 &self,
-                element: &::Element,
+                element: &Self::Type,
                 transition: ::StateChange,
             ) -> Result<::StateChangeSuccess, ::StateChangeError> {
                 let res = self.parent_change_state(element, transition)?;
@@ -706,7 +738,7 @@ mod tests {
     }
 
     glib_wrapper! {
-        pub struct TestElement(ObjectSubclass<imp::TestElement>) @extends ::Element, ::Object;
+        pub struct TestElement(ObjectSubclass<imp::TestElement>) @extends Element, ::Object;
     }
 
     unsafe impl Send for TestElement {}
@@ -735,15 +767,15 @@ mod tests {
         );
 
         let pipeline = ::Pipeline::new(None);
-        let src = ::ElementFactory::make("fakesrc", None).unwrap();
-        let sink = ::ElementFactory::make("fakesink", None).unwrap();
+        let src = ElementFactory::make("fakesrc", None).unwrap();
+        let sink = ElementFactory::make("fakesink", None).unwrap();
 
         src.set_property("num-buffers", &100i32).unwrap();
 
         pipeline
             .add_many(&[&src, &element.upcast_ref(), &sink])
             .unwrap();
-        ::Element::link_many(&[&src, &element.upcast_ref(), &sink]).unwrap();
+        Element::link_many(&[&src, &element.upcast_ref(), &sink]).unwrap();
 
         pipeline.set_state(::State::Playing).unwrap();
         let bus = pipeline.get_bus().unwrap();
diff --git a/gstreamer/src/subclass/pad.rs b/gstreamer/src/subclass/pad.rs
index 89629ed6a..133659407 100644
--- a/gstreamer/src/subclass/pad.rs
+++ b/gstreamer/src/subclass/pad.rs
@@ -9,49 +9,59 @@
 use gst_sys;
 
 use glib;
-use glib::translate::*;
-
+use glib::prelude::*;
 use glib::subclass::prelude::*;
+use glib::translate::*;
 
 use Pad;
 
 pub trait PadImpl: PadImplExt + ObjectImpl + Send + Sync {
-    fn linked(&self, pad: &Pad, peer: &Pad) {
+    fn linked(&self, pad: &Self::Type, peer: &Pad) {
         self.parent_linked(pad, peer)
     }
 
-    fn unlinked(&self, pad: &Pad, peer: &Pad) {
+    fn unlinked(&self, pad: &Self::Type, peer: &Pad) {
         self.parent_unlinked(pad, peer)
     }
 }
 
-pub trait PadImplExt {
-    fn parent_linked(&self, pad: &Pad, peer: &Pad);
+pub trait PadImplExt: ObjectSubclass {
+    fn parent_linked(&self, pad: &Self::Type, peer: &Pad);
 
-    fn parent_unlinked(&self, pad: &Pad, peer: &Pad);
+    fn parent_unlinked(&self, pad: &Self::Type, peer: &Pad);
 }
 
 impl<T: PadImpl> PadImplExt for T {
-    fn parent_linked(&self, pad: &Pad, peer: &Pad) {
+    fn parent_linked(&self, pad: &Self::Type, peer: &Pad) {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstPadClass;
 
             (*parent_class)
                 .linked
-                .map(|f| f(pad.to_glib_none().0, peer.to_glib_none().0))
+                .map(|f| {
+                    f(
+                        pad.unsafe_cast_ref::<Pad>().to_glib_none().0,
+                        peer.to_glib_none().0,
+                    )
+                })
                 .unwrap_or(())
         }
     }
 
-    fn parent_unlinked(&self, pad: &Pad, peer: &Pad) {
+    fn parent_unlinked(&self, pad: &Self::Type, peer: &Pad) {
         unsafe {
             let data = T::type_data();
             let parent_class = data.as_ref().get_parent_class() as *mut gst_sys::GstPadClass;
 
             (*parent_class)
                 .unlinked
-                .map(|f| f(pad.to_glib_none().0, peer.to_glib_none().0))
+                .map(|f| {
+                    f(
+                        pad.unsafe_cast_ref::<Pad>().to_glib_none().0,
+                        peer.to_glib_none().0,
+                    )
+                })
                 .unwrap_or(())
         }
     }
@@ -71,7 +81,7 @@ unsafe extern "C" fn pad_linked<T: PadImpl>(ptr: *mut gst_sys::GstPad, peer: *mu
     let imp = instance.get_impl();
     let wrap: Borrowed<Pad> = from_glib_borrow(ptr);
 
-    imp.linked(&wrap, &from_glib_borrow(peer))
+    imp.linked(wrap.unsafe_cast_ref(), &from_glib_borrow(peer))
 }
 
 unsafe extern "C" fn pad_unlinked<T: PadImpl>(
@@ -82,7 +92,7 @@ unsafe extern "C" fn pad_unlinked<T: PadImpl>(
     let imp = instance.get_impl();
     let wrap: Borrowed<Pad> = from_glib_borrow(ptr);
 
-    imp.unlinked(&wrap, &from_glib_borrow(peer))
+    imp.unlinked(wrap.unsafe_cast_ref(), &from_glib_borrow(peer))
 }
 
 #[cfg(test)]
@@ -93,6 +103,8 @@ mod tests {
     use glib::subclass;
     use std::sync::atomic;
 
+    use PadDirection;
+
     pub mod imp {
         use super::*;
 
@@ -104,7 +116,7 @@ mod tests {
         impl ObjectSubclass for TestPad {
             const NAME: &'static str = "TestPad";
             type Type = super::TestPad;
-            type ParentType = ::Pad;
+            type ParentType = Pad;
             type Instance = subclass::simple::InstanceStruct<Self>;
             type Class = subclass::simple::ClassStruct<Self>;
 
@@ -121,12 +133,12 @@ mod tests {
         impl ObjectImpl for TestPad {}
 
         impl PadImpl for TestPad {
-            fn linked(&self, pad: &Pad, peer: &Pad) {
+            fn linked(&self, pad: &Self::Type, peer: &Pad) {
                 self.linked.store(true, atomic::Ordering::SeqCst);
                 self.parent_linked(pad, peer)
             }
 
-            fn unlinked(&self, pad: &Pad, peer: &Pad) {
+            fn unlinked(&self, pad: &Self::Type, peer: &Pad) {
                 self.unlinked.store(true, atomic::Ordering::SeqCst);
                 self.parent_unlinked(pad, peer)
             }
@@ -134,14 +146,14 @@ mod tests {
     }
 
     glib_wrapper! {
-        pub struct TestPad(ObjectSubclass<imp::TestPad>) @extends ::Pad, ::Object;
+        pub struct TestPad(ObjectSubclass<imp::TestPad>) @extends Pad, ::Object;
     }
 
     unsafe impl Send for TestPad {}
     unsafe impl Sync for TestPad {}
 
     impl TestPad {
-        pub fn new(name: &str, direction: ::PadDirection) -> Self {
+        pub fn new(name: &str, direction: PadDirection) -> Self {
             glib::Object::new(
                 TestPad::static_type(),
                 &[("name", &name), ("direction", &direction)],
@@ -156,11 +168,11 @@ mod tests {
     fn test_pad_subclass() {
         ::init().unwrap();
 
-        let pad = TestPad::new("test", ::PadDirection::Src);
+        let pad = TestPad::new("test", PadDirection::Src);
 
         assert_eq!(pad.get_name(), "test");
 
-        let otherpad = ::Pad::new(Some("other-test"), ::PadDirection::Sink);
+        let otherpad = Pad::new(Some("other-test"), PadDirection::Sink);
         pad.link(&otherpad).unwrap();
         pad.unlink(&otherpad).unwrap();
 
diff --git a/gstreamer/src/subclass/uri_handler.rs b/gstreamer/src/subclass/uri_handler.rs
index d37c66da8..27620e9a3 100644
--- a/gstreamer/src/subclass/uri_handler.rs
+++ b/gstreamer/src/subclass/uri_handler.rs
@@ -21,8 +21,8 @@ use URIHandler;
 use URIType;
 
 pub trait URIHandlerImpl: super::element::ElementImpl {
-    fn get_uri(&self, element: &URIHandler) -> Option<String>;
-    fn set_uri(&self, element: &URIHandler, uri: &str) -> Result<(), glib::Error>;
+    fn get_uri(&self, element: &Self::Type) -> Option<String>;
+    fn set_uri(&self, element: &Self::Type, uri: &str) -> Result<(), glib::Error>;
     fn get_uri_type() -> URIType;
     fn get_protocols() -> Vec<String>;
 }
@@ -72,7 +72,8 @@ unsafe extern "C" fn uri_handler_get_uri<T: URIHandlerImpl>(
     let instance = &*(uri_handler as *mut T::Instance);
     let imp = instance.get_impl();
 
-    imp.get_uri(&from_glib_borrow(uri_handler)).to_glib_full()
+    imp.get_uri(&from_glib_borrow::<_, URIHandler>(uri_handler).unsafe_cast_ref())
+        .to_glib_full()
 }
 
 unsafe extern "C" fn uri_handler_set_uri<T: URIHandlerImpl>(
@@ -84,7 +85,7 @@ unsafe extern "C" fn uri_handler_set_uri<T: URIHandlerImpl>(
     let imp = instance.get_impl();
 
     match imp.set_uri(
-        &from_glib_borrow(uri_handler),
+        &from_glib_borrow::<_, URIHandler>(uri_handler).unsafe_cast_ref(),
         glib::GString::from_glib_borrow(uri).as_str(),
     ) {
         Ok(()) => true.to_glib(),