diff --git a/Database/Persist/MongoDB.hs b/Database/Persist/MongoDB.hs
--- a/Database/Persist/MongoDB.hs
+++ b/Database/Persist/MongoDB.hs
@@ -361,7 +361,7 @@
       Just doc -> Right doc
     Just e -> Left e
     where
-      findErr result = DB.lookup "err" (DB.at "lastErrorObject" result)
+      findErr result = DB.lookup "err" =<< (DB.lookup "lastErrorObject" result)
 
 instance (Applicative m, Functor m, Trans.MonadIO m, MonadBaseControl IO m) => PersistQuery (DB.Action m) where
     update _ [] = return ()
@@ -687,7 +687,8 @@
 dummyFromFilts :: [Filter v] -> v
 dummyFromFilts _ = error "dummyFromFilts"
 
-data MongoAuth = MongoAuth DB.Username DB.Password
+data MongoAuth = MongoAuth DB.Username DB.Password deriving Show
+
 -- | Information required to connect to a mongo database
 data MongoConf = MongoConf
     { mgDatabase :: Text
@@ -698,7 +699,7 @@
     , mgPoolStripes :: Int
     , mgStripeConnections :: Int
     , mgConnectionIdleTime :: NominalDiffTime
-    }
+    } deriving Show
 
 instance PersistConfig MongoConf where
     type PersistConfigBackend MongoConf = DB.Action
diff --git a/persistent-mongoDB.cabal b/persistent-mongoDB.cabal
--- a/persistent-mongoDB.cabal
+++ b/persistent-mongoDB.cabal
@@ -1,5 +1,5 @@
 name:            persistent-mongoDB
-version:         1.2.0
+version:         1.2.0.1
 license:         MIT
 license-file:    LICENSE
 author:          Greg Weber <greg@gregweber.info>