diff --git a/lib/ace/tokenizer.js b/lib/ace/tokenizer.js
index 6ed271b1..f7f7f02e 100644
--- a/lib/ace/tokenizer.js
+++ b/lib/ace/tokenizer.js
@@ -93,7 +93,7 @@ var Tokenizer = function(rules) {
                     matchcount = 1;
                     adjustedregex = this.removeCapturingGroups(rule.regex);
                 }
-                if (!rule.splitRegex)
+                if (!rule.splitRegex && typeof rule.token != "string")
                     rule.splitRegex = this.createSplitterRegexp(rule.regex, flag);
             }
 
@@ -139,7 +139,34 @@ var Tokenizer = function(rules) {
     };
     
     this.createSplitterRegexp = function(src, flag) {
-        src = src.replace(/\(\?=([^()]|\\.|\(([^()]|\\.)*?\))*\)(?=\)*$)/, "");
+        if (src.indexOf("(?=") != -1) {
+            var stack = 0;
+            var inChClass = false;
+            var lastCapture = {};
+            src.replace(/(\\.)|(\((?:\?[=!])?)|(\))|([])/g, function(
+                m, esc, parenOpen, parenClose, square, index
+            ) {
+                if (inChClass) {
+                    inChClass = square != "]";
+                } else if (square) {
+                    inChClass = true;
+                } else if (parenClose) {
+                    if (stack == lastCapture.stack)
+                        lastCapture.end = index+1
+                    stack--;
+                } else if (parenOpen) {
+                    stack++;
+                    if (parenOpen.length != 1) {
+                        lastCapture.stack = stack
+                        lastCapture.start = index;
+                    }
+                }
+                return m;
+            });
+
+            if (lastCapture.end != null && /^\)*$/.test(src.substr(lastCapture.end)))
+                src = src.substring(0, lastCapture.start) + src.substr(lastCapture.end);
+        }
         return new RegExp(src, (flag||"").replace("g", ""));
     };