diff --git a/lib/ace/tokenizer.js b/lib/ace/tokenizer.js
index 66e9b847..105c14c9 100644
--- a/lib/ace/tokenizer.js
+++ b/lib/ace/tokenizer.js
@@ -76,7 +76,7 @@ var Tokenizer = function(rules) {
             var value = match[0];
 
             for ( var i = 0; i < state.length; i++) {
-                if (match[i + 1]) {
+                if (match[i + 1] !== undefined) {
                     var rule = state[i];
                     
                     if (typeof rule.token == "function")