diff --git a/lib/ace/lib/useragent.js b/lib/ace/lib/useragent.js
index e539dae3..0d1d9f4d 100644
--- a/lib/ace/lib/useragent.js
+++ b/lib/ace/lib/useragent.js
@@ -82,7 +82,7 @@ exports.isIE =
 exports.isOldIE = exports.isIE && exports.isIE < 9;
 
 // Is this Firefox or related?
-exports.isGecko = exports.isMozilla = window.controllers && window.navigator.product === "Gecko";
+exports.isGecko = exports.isMozilla = (window.Controllers || window.controllers) && window.navigator.product === "Gecko";
 
 // oldGecko == rev < 2.0 
 exports.isOldGecko = exports.isGecko && parseInt((ua.match(/rv\:(\d+)/)||[])[1], 10) < 4;