diff --git a/gstreamer-app/src/app_sink.rs b/gstreamer-app/src/app_sink.rs
index 4c4e38f9f..b81e5138a 100644
--- a/gstreamer-app/src/app_sink.rs
+++ b/gstreamer-app/src/app_sink.rs
@@ -271,6 +271,7 @@ impl AppSink {
     ///
     /// This method returns an instance of [`AppSinkBuilder`](crate::builders::AppSinkBuilder) which can be used to create [`AppSink`] objects.
     pub fn builder() -> AppSinkBuilder {
+        assert_initialized_main_thread!();
         AppSinkBuilder::default()
     }
 
diff --git a/gstreamer-app/src/app_src.rs b/gstreamer-app/src/app_src.rs
index 2b04f179c..fd9e0fded 100644
--- a/gstreamer-app/src/app_src.rs
+++ b/gstreamer-app/src/app_src.rs
@@ -216,6 +216,7 @@ impl AppSrc {
     ///
     /// This method returns an instance of [`AppSrcBuilder`](crate::builders::AppSrcBuilder) which can be used to create [`AppSrc`] objects.
     pub fn builder() -> AppSrcBuilder {
+        assert_initialized_main_thread!();
         AppSrcBuilder::default()
     }