--- a/src/bubble-window.c
+++ b/src/bubble-window.c
@@ -78,8 +78,8 @@ bubble_window_get_accessible (GtkWidget
     {
       AtkObjectFactory *factory = NULL;
       AtkRegistry *registry = NULL;
-      GType derived_type = NULL;
-      GType derived_atk_type = NULL;
+      GType derived_type = G_TYPE_INVALID;
+      GType derived_atk_type = G_TYPE_INVALID;
 
       /*
        * Figure out whether accessibility is enabled by looking at the
--- a/src/display.c
+++ b/src/display.c
@@ -288,7 +288,7 @@ stack_layout (Stack* self)
 	gint       y      = 0;
 	gint       x      = 0;
 
-	g_return_if_fail (self != NULL);
+	g_return_val_if_fail (self != NULL, TRUE);
 
 	bubble = stack_select_next_to_display (self);
 	if (bubble == NULL)