diff --git a/gir-files/Gst-1.0.gir b/gir-files/Gst-1.0.gir
index db0ea9cea..21e38564b 100644
--- a/gir-files/Gst-1.0.gir
+++ b/gir-files/Gst-1.0.gir
@@ -38017,7 +38017,10 @@ MT safe.</doc>
           <type name="none" c:type="void"/>
         </return-value>
         <parameters>
-          <parameter name="new_clock" transfer-ownership="none">
+          <parameter name="new_clock"
+                     transfer-ownership="none"
+                     nullable="1"
+                     allow-none="1">
             <doc xml:space="preserve">a #GstClock</doc>
             <type name="Clock" c:type="GstClock*"/>
           </parameter>
diff --git a/gstreamer/src/auto/system_clock.rs b/gstreamer/src/auto/system_clock.rs
index da45d21b1..a292acd53 100644
--- a/gstreamer/src/auto/system_clock.rs
+++ b/gstreamer/src/auto/system_clock.rs
@@ -36,10 +36,12 @@ impl SystemClock {
         }
     }
 
-    pub fn set_default<P: IsA<Clock>>(new_clock: &P) {
-        skip_assert_initialized!();
+    pub fn set_default<'a, P: IsA<Clock> + 'a, Q: Into<Option<&'a P>>>(new_clock: Q) {
+        assert_initialized_main_thread!();
+        let new_clock = new_clock.into();
+        let new_clock = new_clock.to_glib_none();
         unsafe {
-            ffi::gst_system_clock_set_default(new_clock.to_glib_none().0);
+            ffi::gst_system_clock_set_default(new_clock.0);
         }
     }
 }