diff --git a/marco-wrapper b/marco-wrapper
index 6342ce0..7cd4ba9 100755
--- a/marco-wrapper
+++ b/marco-wrapper
@@ -76,7 +76,7 @@ if [ -n "${COMP}" ]; then
             --shadow-exclude "class_g = 'albert'" \
             --shadow-exclude "class_g = 'Cairo-clock'" \
             --shadow-exclude "class_g = 'Conky'" \
-            --shadow-exclude "class_g = 'Firefox' && argb" \
+            --shadow-exclude "class_g ?= 'Firefox' && argb" \
             --shadow-exclude "class_g ?= 'Notify-osd'" \
             --shadow-exclude "class_g = 'Synapse'" \
             --shadow-exclude "class_g = 'Ulauncher'" \