diff --git a/ext/cog/gstcogdownsample.c b/ext/cog/gstcogdownsample.c
index 5d6b4f9ed3..8bec086c01 100644
--- a/ext/cog/gstcogdownsample.c
+++ b/ext/cog/gstcogdownsample.c
@@ -357,6 +357,7 @@ gst_cogdownsample_transform (GstBaseTransform * base_transform,
       break;
     default:
       g_assert_not_reached ();
+      return GST_FLOW_ERROR;
   }
 
   frame = cog_virt_frame_new_unpack (frame);
diff --git a/ext/cog/gstcogutils.c b/ext/cog/gstcogutils.c
index 4d7c8b99f0..ff23862f88 100644
--- a/ext/cog/gstcogutils.c
+++ b/ext/cog/gstcogutils.c
@@ -126,6 +126,7 @@ gst_cog_buffer_wrap (GstBuffer * buf, GstVideoFormat format, int width,
       break;
     default:
       g_assert_not_reached ();
+      return NULL;
   }
   cog_frame_set_free_callback (frame, gst_cog_frame_free, buf);
 
diff --git a/ext/schroedinger/gstschroenc.c b/ext/schroedinger/gstschroenc.c
index b4e50a922c..7af28eac2a 100644
--- a/ext/schroedinger/gstschroenc.c
+++ b/ext/schroedinger/gstschroenc.c
@@ -600,6 +600,7 @@ gst_schro_enc_get_caps (GstBaseVideoEncoder * base_video_encoder)
         state->par_d, NULL);
   } else {
     g_assert_not_reached ();
+    caps = NULL;
   }
 
   return caps;
diff --git a/ext/schroedinger/gstschroparse.c b/ext/schroedinger/gstschroparse.c
index 25711c8d14..a734f2dc53 100644
--- a/ext/schroedinger/gstschroparse.c
+++ b/ext/schroedinger/gstschroparse.c
@@ -579,6 +579,7 @@ gst_schro_parse_get_caps (GstBaseVideoParse * base_video_parse)
         state->par_d, NULL);
   } else {
     g_assert_not_reached ();
+    caps = NULL;
   }
 
   return caps;
diff --git a/ext/schroedinger/gstschroutils.c b/ext/schroedinger/gstschroutils.c
index bb1f1bcd62..66514a3d53 100644
--- a/ext/schroedinger/gstschroutils.c
+++ b/ext/schroedinger/gstschroutils.c
@@ -95,6 +95,7 @@ gst_schro_buffer_wrap (GstBuffer * buf, GstVideoFormat format, int width,
 #endif
     default:
       g_assert_not_reached ();
+      return NULL;
   }
   schro_frame_set_free_callback (frame, gst_schro_frame_free, buf);