diff --git a/src/window.c b/src/window.c
index 74ab775..97e91e7 100644
--- a/src/window.c
+++ b/src/window.c
@@ -3077,6 +3077,7 @@ findLowestSiblingBelow (CompWindow *w)
 	switch (type) {
 	case CompWindowTypeDesktopMask:
 	    /* desktop window layer */
+	    return NULL;
 	    break;
 	case CompWindowTypeFullscreenMask:
 	case CompWindowTypeDockMask: