diff --git a/cogl/cogl/cogl-bitmap-conversion.c b/cogl/cogl/cogl-bitmap-conversion.c
index 9d20a47df..f1b91cee3 100644
--- a/cogl/cogl/cogl-bitmap-conversion.c
+++ b/cogl/cogl/cogl-bitmap-conversion.c
@@ -355,6 +355,7 @@ _cogl_bitmap_needs_short_temp_buffer (CoglPixelFormat format)
     }
 
   g_assert_not_reached ();
+  return FALSE;
 }
 
 CoglBool
diff --git a/cogl/cogl/driver/gl/cogl-buffer-gl.c b/cogl/cogl/driver/gl/cogl-buffer-gl.c
index 6f542d5dd..871a6ff84 100644
--- a/cogl/cogl/driver/gl/cogl-buffer-gl.c
+++ b/cogl/cogl/driver/gl/cogl-buffer-gl.c
@@ -112,6 +112,7 @@ update_hints_to_gl_enum (CoglBuffer *buffer)
     }
 
   g_assert_not_reached ();
+  return 0;
 }
 
 static GLenum
diff --git a/cogl/cogl/winsys/cogl-winsys-egl.c b/cogl/cogl/winsys/cogl-winsys-egl.c
index 222e5a6e7..8153f3579 100644
--- a/cogl/cogl/winsys/cogl-winsys-egl.c
+++ b/cogl/cogl/winsys/cogl-winsys-egl.c
@@ -135,6 +135,7 @@ get_error_string (void)
      return "Invalid surface";
   default:
     g_assert_not_reached ();
+    return NULL;
   }
 }
 
@@ -219,6 +220,7 @@ _cogl_winsys_renderer_connect (CoglRenderer *renderer,
 {
   /* This function must be overridden by a platform winsys */
   g_assert_not_reached ();
+  return FALSE;
 }
 
 static void
diff --git a/cogl/tests/conform/test-point-size-attribute.c b/cogl/tests/conform/test-point-size-attribute.c
index 538f26a0f..5bc605142 100644
--- a/cogl/tests/conform/test-point-size-attribute.c
+++ b/cogl/tests/conform/test-point-size-attribute.c
@@ -30,6 +30,7 @@ calc_coord_offset (int pos, int pos_index, int point_size)
     }
 
   g_assert_not_reached ();
+  return 0;
 }
 
 static void
diff --git a/cogl/tests/conform/test-point-size.c b/cogl/tests/conform/test-point-size.c
index c64b7e266..c25840e9a 100644
--- a/cogl/tests/conform/test-point-size.c
+++ b/cogl/tests/conform/test-point-size.c
@@ -22,6 +22,7 @@ calc_coord_offset (int pos, int pos_index, int point_size)
     }
 
   g_assert_not_reached ();
+  return 0;
 }
 
 static void