diff --git a/lib/firefox_profile.js b/lib/firefox_profile.js
index 9bafcd1..71561a3 100644
--- a/lib/firefox_profile.js
+++ b/lib/firefox_profile.js
@@ -527,7 +527,7 @@ FirefoxProfile.prototype._writeUserPrefs = function(userPrefs) {
 
 FirefoxProfile.prototype._readExistingUserjs = function() {
   var self = this,
-      regExp = /user_pref\(['"](.*)["'],\s*['"]?(.*)["']?\)/,
+      regExp = /user_pref\(['"](.*)["'],\s*(.*)\)/,
       contentLines = fs.readFileSync(this.userPrefs, "utf8").split('\n');
   contentLines.forEach(function(line) {
     var found = line.match(regExp);