diff --git a/extensions/firefox/content/PdfStreamConverter.jsm b/extensions/firefox/content/PdfStreamConverter.jsm
index dd052a1e80af2..9ff5d4dc865b6 100644
--- a/extensions/firefox/content/PdfStreamConverter.jsm
+++ b/extensions/firefox/content/PdfStreamConverter.jsm
@@ -93,7 +93,12 @@ function getIntPref(pref, def) {
 
 function getStringPref(pref, def) {
   try {
-    return Services.prefs.getComplexValue(pref, Ci.nsISupportsString).data;
+//#if !MOZCENTRAL
+    if (!Services.prefs.getStringPref) {
+      return Services.prefs.getComplexValue(pref, Ci.nsISupportsString).data;
+    }
+//#endif
+    return Services.prefs.getStringPref(pref);
   } catch (ex) {
     return def;
   }
diff --git a/extensions/firefox/content/PdfjsChromeUtils.jsm b/extensions/firefox/content/PdfjsChromeUtils.jsm
index 1d6c3f8af707a..f6e7e44c73c4d 100644
--- a/extensions/firefox/content/PdfjsChromeUtils.jsm
+++ b/extensions/firefox/content/PdfjsChromeUtils.jsm
@@ -273,10 +273,16 @@ var PdfjsChromeUtils = {
 
   _setStringPref(aPrefName, aPrefValue) {
     this._ensurePreferenceAllowed(aPrefName);
-    let str = Cc["@mozilla.org/supports-string;1"]
-                .createInstance(Ci.nsISupportsString);
-    str.data = aPrefValue;
-    Services.prefs.setComplexValue(aPrefName, Ci.nsISupportsString, str);
+//#if !MOZCENTRAL
+    if (!Services.prefs.setStringPref) {
+      let str = Cc["@mozilla.org/supports-string;1"]
+                  .createInstance(Ci.nsISupportsString);
+      str.data = aPrefValue;
+      Services.prefs.setComplexValue(aPrefName, Ci.nsISupportsString, str);
+      return;
+    }
+//#endif
+    Services.prefs.setStringPref(aPrefName, aPrefValue);
   },
 
   /*