--- a/browser/themes/shared/customizableui/customizeMode.inc.css
+++ b/browser/themes/shared/customizableui/customizeMode.inc.css
@@ -116,17 +116,17 @@
 }
 
 #customization-palette,
 #customization-empty {
   padding: 5px 20px 20px;
 }
 
 #customization-header {
-%ifdef MOZ_PHOTON_THEME;
+%ifndef MOZ_PHOTON_THEME
   border-bottom: 1px solid ThreeDLightShadow;
   font-size: 1.75em;
   line-height: 1.75em;
   color: GrayText;
   font-weight: 200;
   padding-bottom: 12px;
 %else
   font-weight: 600;