diff --git a/lib/ace/mode/text_highlight_rules.js b/lib/ace/mode/text_highlight_rules.js
index 660e1308..2dd176f4 100644
--- a/lib/ace/mode/text_highlight_rules.js
+++ b/lib/ace/mode/text_highlight_rules.js
@@ -81,9 +81,11 @@ var TextHighlightRules = function() {
         
         this.addRules(embedRules, prefix);
 
-        var addRules = Array.prototype[append ? "push" : "unshift"];
-        for (var i = 0; i < states.length; i++)
-            addRules.apply(this.$rules[states[i]], lang.deepCopy(escapeRules));       
+        if (escapeRules) {
+            var addRules = Array.prototype[append ? "push" : "unshift"];
+            for (var i = 0; i < states.length; i++)
+                addRules.apply(this.$rules[states[i]], lang.deepCopy(escapeRules));
+        }
 
         if (!this.$embeds)
             this.$embeds = [];