diff --git a/extensions/firefox/content/PdfJs.jsm b/extensions/firefox/content/PdfJs.jsm
index b86cbbcda06d6..0f8e676b91826 100644
--- a/extensions/firefox/content/PdfJs.jsm
+++ b/extensions/firefox/content/PdfJs.jsm
@@ -181,11 +181,11 @@ var PdfJs = {
 
   uninit: function uninit() {
     if (this._initialized) {
-      Services.prefs.removeObserver(PREF_DISABLED, this, false);
-      Services.prefs.removeObserver(PREF_DISABLED_PLUGIN_TYPES, this, false);
-      Services.obs.removeObserver(this, TOPIC_PDFJS_HANDLER_CHANGED, false);
-      Services.obs.removeObserver(this, TOPIC_PLUGINS_LIST_UPDATED, false);
-      Services.obs.removeObserver(this, TOPIC_PLUGIN_INFO_UPDATED, false);
+      Services.prefs.removeObserver(PREF_DISABLED, this);
+      Services.prefs.removeObserver(PREF_DISABLED_PLUGIN_TYPES, this);
+      Services.obs.removeObserver(this, TOPIC_PDFJS_HANDLER_CHANGED);
+      Services.obs.removeObserver(this, TOPIC_PLUGINS_LIST_UPDATED);
+      Services.obs.removeObserver(this, TOPIC_PLUGIN_INFO_UPDATED);
       this._initialized = false;
     }
     this._ensureUnregistered();
diff --git a/extensions/firefox/content/PdfjsChromeUtils.jsm b/extensions/firefox/content/PdfjsChromeUtils.jsm
index 16bb0d9cad6af..fccbd88b3ee18 100644
--- a/extensions/firefox/content/PdfjsChromeUtils.jsm
+++ b/extensions/firefox/content/PdfjsChromeUtils.jsm
@@ -94,7 +94,7 @@ var PdfjsChromeUtils = {
       this._mmg.removeMessageListener('PDFJS:Parent:removeEventListener', this);
       this._mmg.removeMessageListener('PDFJS:Parent:updateControlState', this);
 
-      Services.obs.removeObserver(this, 'quit-application', false);
+      Services.obs.removeObserver(this, 'quit-application');
 
       this._mmg = null;
       this._ppmm = null;