diff --git a/xulrunner/setup/nsXULAppInstall.js b/xulrunner/setup/nsXULAppInstall.js
index 281f962e21d..06c505ed2b7 100644
--- a/xulrunner/setup/nsXULAppInstall.js
+++ b/xulrunner/setup/nsXULAppInstall.js
@@ -247,7 +247,8 @@ const AppInstall = {
       aDirectory = Components.classes["@mozilla.org/file/local;1"].
         createInstance(nsILocalFile);
       aDirectory.initWithPath("/usr/lib");
-      aDirectory.append(vendor.toLowerCase());
+      if (vendor)
+        aDirectory.append(vendor.toLowerCase());
 #endif
 #endif
     }