diff --git a/lib/ace/lib/event.js b/lib/ace/lib/event.js
index 1afca2a2..0948f158 100644
--- a/lib/ace/lib/event.js
+++ b/lib/ace/lib/event.js
@@ -292,7 +292,7 @@ exports.addCommandKeyListener = function(el, callback) {
     }
 };
 
-if (window.postMessage) {
+if (window.postMessage && !useragent.isOldIE) {
     var postMessageId = 1;
     exports.nextTick = function(callback, win) {
         win = win || window;