diff --git a/browser/base/content/aboutDialog.js b/browser/base/content/aboutDialog.js
index 461375ec3bd..23f2e70d04a 100644
--- a/browser/base/content/aboutDialog.js
+++ b/browser/base/content/aboutDialog.js
@@ -497,7 +497,9 @@ appUpdater.prototype =
   },
 
   removeDownloadListener: function() {
-    this.aus.removeDownloadListener(this);
+    if (this.aus) {
+      this.aus.removeDownloadListener(this);
+    }
   },
 
   /**