diff --git a/config.def.h b/config.def.h
index b0ce018..a3441e1 100644
--- a/config.def.h
+++ b/config.def.h
@@ -36,7 +36,10 @@ static const Rule rules[] = {
 	 */
 	/* class      instance    title       tags mask     iscentered   isfloating   monitor */
 	{ "Gimp",     NULL,       NULL,       0,            0,           1,           -1 },
-	{ "Firefox",  NULL,       NULL,       0,            0,           0,           -1 },
+	{ "Firefox",  NULL,       NULL,       0,            1,           0,           -1 },
+	{ "firefox",  NULL,       NULL,       0,            1,           0,           -1 },
+	{ "St",       NULL,       NULL,       0,            1,           0,           -1 },
+	{ "Gcr-prompt", NULL,     NULL,       0,            1,           0,           -1 },
 };
 
 /* layout(s) */