diff --git a/extensions/firefox/bootstrap.js b/extensions/firefox/bootstrap.js
index af9c5c1b2..5bf66d444 100644
--- a/extensions/firefox/bootstrap.js
+++ b/extensions/firefox/bootstrap.js
@@ -13,16 +13,16 @@ let Cu = Components.utils;
 
 Cu.import('resource://gre/modules/Services.jsm');
 
-function getBoolPref(pref, default) {
+function getBoolPref(pref, def) {
   try {
     return Services.prefs.getBoolPref(pref);
   } catch (ex) {
-    return default;
+    return def;
   }
 }
 
 function setStringPref(pref, value) {
-  let str = Cc["@mozilla.org/supports-string;1"]
+  let str = Cc['@mozilla.org/supports-string;1']
               .createInstance(Ci.nsISupportsString);
   str.data = value;
   Services.prefs.setComplexValue(pref, Ci.nsISupportsString, str);
diff --git a/extensions/firefox/components/PdfStreamConverter.js b/extensions/firefox/components/PdfStreamConverter.js
index bfffd0bc1..deeb112f6 100644
--- a/extensions/firefox/components/PdfStreamConverter.js
+++ b/extensions/firefox/components/PdfStreamConverter.js
@@ -21,26 +21,26 @@ let privateBrowsing = Cc['@mozilla.org/privatebrowsing;1']
                         .getService(Ci.nsIPrivateBrowsingService);
 let inPrivateBrowswing = privateBrowsing.privateBrowsingEnabled;
 
-function getBoolPref(pref, default) {
+function getBoolPref(pref, def) {
   try {
     return Services.prefs.getBoolPref(pref);
   } catch (ex) {
-    return default;
+    return def;
   }
 }
 
 function setStringPref(pref, value) {
-  let str = Cc["@mozilla.org/supports-string;1"]
+  let str = Cc['@mozilla.org/supports-string;1']
               .createInstance(Ci.nsISupportsString);
   str.data = value;
   Services.prefs.setComplexValue(pref, Ci.nsISupportsString, str);
 }
 
-function getStringPref(pref, default) {
+function getStringPref(pref, def) {
   try {
     return Services.prefs.getComplexValue(pref, Ci.nsISupportsString).data;
   } catch (ex) {
-    return default;
+    return def;
   }
 }