diff --git a/lib/ace/mode/lua.js b/lib/ace/mode/lua.js
index e1a6143a..91d85de8 100644
--- a/lib/ace/mode/lua.js
+++ b/lib/ace/mode/lua.js
@@ -66,7 +66,7 @@ oop.inherits(Mode, TextMode);
         var level = 0;
         // Support single-line blocks by decrementing the indent level if
         // an ending token is found
-        for (var i in tokens){
+        for (var i = 0; i < tokens.length; i++) {
             var token = tokens[i];
             if (token.type == "keyword") {
                 if (token.value in indentKeywords) {