diff --git a/mode/css/css.js b/mode/css/css.js
index 02cc93d9cf..7f8c46ebb6 100644
--- a/mode/css/css.js
+++ b/mode/css/css.js
@@ -748,8 +748,8 @@ CodeMirror.defineMode("css", function(config, parserConfig) {
         }
       },
       ":": function(stream) {
-        if (stream.match(/\s*\{/))
-          return [null, "{"];
+        if (stream.match(/\s*\{/, false))
+          return [null, null]
         return false;
       },
       "$": function(stream) {