diff --git a/src/appicon.c b/src/appicon.c
index 1d28a245..ed03ffc1 100644
--- a/src/appicon.c
+++ b/src/appicon.c
@@ -126,7 +126,7 @@ WAppIcon *wAppIconCreateForDock(WScreen *scr, const char *command, const char *w
 	if (wm_instance)
 		aicon->wm_instance = wstrdup(wm_instance);
 
-	if (strcmp(wm_class, "WMDock") == 0 && wPreferences.flags.clip_merged_in_dock)
+	if (wPreferences.flags.clip_merged_in_dock && wm_class != NULL && strcmp(wm_class, "WMDock") == 0)
 		tile = TILE_CLIP;
 	aicon->icon = icon_create_for_dock(scr, command, wm_instance, wm_class, tile);