diff --git a/layout.c b/layout.c
index d356560a7..0dc9b4ce2 100644
--- a/layout.c
+++ b/layout.c
@@ -102,6 +102,7 @@ layout_refresh(void *v __attribute__ ((unused)))
     for(screen = 0; screen < globalconf.screens_info->nscreen; screen++)
         if(globalconf.screens[screen].need_arrange)
             arrange(screen);
+    return NULL;
 }
 
 /** Get current layout used on screen.