--- a/dom/base/nsMimeTypeArray.cpp
+++ b/dom/base/nsMimeTypeArray.cpp
@@ -248,27 +248,27 @@ nsresult nsMimeTypeArray::GetMimeTypes()
       if (!mMimeTypeArray.SetCapacity(pluginMimeTypeCount))
         return NS_ERROR_OUT_OF_MEMORY;
 
       mPluginMimeTypeCount = pluginMimeTypeCount;
       mInited = PR_TRUE;
 
       PRUint32 k;
       for (k = 0; k < pluginCount; k++) {
-        nsIDOMPlugin* plugin = nsnull;
-        if (pluginArray->Item(k, &plugin) == NS_OK) {
+        nsCOMPtr<nsIDOMPlugin> plugin;
+        if (NS_SUCCEEDED(pluginArray->Item(k, getter_AddRefs(plugin))) &&
+            plugin) {
           PRUint32 mimeTypeCount = 0;
           if (plugin->GetLength(&mimeTypeCount) == NS_OK) {
             nsCOMPtr<nsIDOMMimeType> item;
             for (PRUint32 j = 0; j < mimeTypeCount; j++) {
               plugin->Item(j, getter_AddRefs(item));
               mMimeTypeArray.AppendObject(item);
             }
           }
-          NS_RELEASE(plugin);
         }
       }
     }
     NS_RELEASE(pluginArray);
   }
   return rv;
 }