diff --git a/serversession-backend-acid-state/src/Web/ServerSession/Backend/Acid/Internal.hs b/serversession-backend-acid-state/src/Web/ServerSession/Backend/Acid/Internal.hs
index a7267fa..bc0f452 100644
--- a/serversession-backend-acid-state/src/Web/ServerSession/Backend/Acid/Internal.hs
+++ b/serversession-backend-acid-state/src/Web/ServerSession/Backend/Acid/Internal.hs
@@ -259,11 +259,11 @@ instance ( SS.IsSessionData sess
 -- makeAcidic can't handle type variables, so we have to do
 -- everything by hand. :(
 
-data GetSession sess = GetSession (SS.SessionId sess)
-data DeleteSession sess = DeleteSession (SS.SessionId sess)
-data DeleteAllSessionsOfAuthId sess = DeleteAllSessionsOfAuthId SS.AuthId
-data InsertSession sess = InsertSession (SS.Session sess)
-data ReplaceSession sess = ReplaceSession (SS.Session sess)
+data GetSession sess = GetSession (SS.SessionId sess) deriving (Typeable)
+data DeleteSession sess = DeleteSession (SS.SessionId sess) deriving (Typeable)
+data DeleteAllSessionsOfAuthId sess = DeleteAllSessionsOfAuthId SS.AuthId deriving (Typeable)
+data InsertSession sess = InsertSession (SS.Session sess) deriving (Typeable)
+data ReplaceSession sess = ReplaceSession (SS.Session sess) deriving (Typeable)
 
 instance SafeCopy (GetSession sess) where
   putCopy (GetSession v) = contain $ safePut v
diff --git a/serversession-backend-persistent/src/Web/ServerSession/Backend/Persistent/Internal/Impl.hs b/serversession-backend-persistent/src/Web/ServerSession/Backend/Persistent/Internal/Impl.hs
index 8b83c2f..e3e79b5 100644
--- a/serversession-backend-persistent/src/Web/ServerSession/Backend/Persistent/Internal/Impl.hs
+++ b/serversession-backend-persistent/src/Web/ServerSession/Backend/Persistent/Internal/Impl.hs
@@ -15,6 +15,7 @@ module Web.ServerSession.Backend.Persistent.Internal.Impl
 import Control.Applicative ((<$>), (<*>))
 import Control.Monad (void)
 import Control.Monad.IO.Class (liftIO)
+import Data.Monoid (mempty)
 import Data.Proxy (Proxy(..))
 import Data.Time (UTCTime)
 import Data.Typeable (Typeable)