diff --git a/src/css/CSS.js b/src/css/CSS.js
index efdd903f4..dff1cf740 100644
--- a/src/css/CSS.js
+++ b/src/css/CSS.js
@@ -26,10 +26,10 @@ sub: function(css) {
     var words = name.slice(1).split('$');
     var sel = variables;
     for (var i = 0; i < words.length; i++) {
-      if (typeof sel !== 'object') return name;
+      if (typeof sel !== 'object') return ':not(*)';
       sel = sel[words[i]];
     }
-    if (typeof sel !== 'string') return name;
+    if (typeof sel !== 'string') return ':not(*)';
     return sel;
   });
 }