       return
     return
 
-  unstore: (doc, onSuccess, onError) ->
+  unstore: (doc, onSuccess, onError, _retry = true) ->
     @db (db) =>
       unless db
         onError()

        return
      txn.onerror = (event) ->
        event.preventDefault()
        onError(event)
        return

      store = txn.objectStore(doc.slug)

        @cachedDocs?[doc.slug] = doc.mtime
        onSuccess()
        return
      txn.onerror = (event) =>
        event.preventDefault()
        if txn.error.name is 'NotFoundError' and _retry
          @migrate()
          @store(doc, data, onSuccess, onError, false)
        else
          onError(event)
        return

      store = txn.objectStore(doc.slug)
