diff --git a/happstack-server.cabal b/happstack-server.cabal
--- a/happstack-server.cabal
+++ b/happstack-server.cabal
@@ -1,5 +1,5 @@
 Name:                happstack-server
-Version:             7.8.0.1
+Version:             7.8.0.2
 Synopsis:            Web related tools and services.
 Description:         Happstack Server provides an HTTP server and a rich set of functions for routing requests, handling query parameters, generating responses, working with cookies, serving files, and more. For in-depth documentation see the Happstack Crash Course <http://happstack.com/docs/crashcourse/index.html>
 License:             BSD3
@@ -11,7 +11,7 @@
 Build-Type:          Simple
 Cabal-Version:       >= 1.10
 Extra-Source-Files:  tests/Happstack/Server/Tests.hs README.md
-tested-with:         GHC==8.0.2, GHC==8.2.2, GHC==8.4.4, GHC==8.6.5, GHC==8.8.4, GHC==8.10.7, GHC==9.0.2, GHC==9.2.2
+tested-with:         GHC==8.0.2, GHC==8.2.2, GHC==8.4.4, GHC==8.6.5, GHC==8.8.4, GHC==8.10.7, GHC==9.0.2, GHC==9.2.5, GHC==9.4.3
 
 source-repository head
     type:     git
diff --git a/src/Happstack/Server/Internal/Monads.hs b/src/Happstack/Server/Internal/Monads.hs
--- a/src/Happstack/Server/Internal/Monads.hs
+++ b/src/Happstack/Server/Internal/Monads.hs
@@ -12,8 +12,8 @@
                                                  )
 import Control.Monad.Base                        ( MonadBase, liftBase )
 import Control.Monad.Catch                       ( MonadCatch(..), MonadThrow(..) )
-#if !MIN_VERSION_mtl(2,3,0)
-import Control.Monad.Error                       ( ErrorT, Error, mapErrorT )
+#if !MIN_VERSION_transformers(0,6,0)
+import Control.Monad.Trans.Error                 ( ErrorT, Error, mapErrorT )
 #endif
 import Control.Monad.Except                      ( MonadError, throwError
                                                  , catchError
@@ -756,7 +756,7 @@
 
 -- ErrorT
 
-#if !MIN_VERSION_mtl(2,3,0)
+#if !MIN_VERSION_transformers(0,6,0)
 instance (Error e, ServerMonad m) => ServerMonad (ErrorT e m) where
     askRq     = lift askRq
     localRq f = mapErrorT $ localRq f
diff --git a/src/Happstack/Server/Internal/Types.hs b/src/Happstack/Server/Internal/Types.hs
--- a/src/Happstack/Server/Internal/Types.hs
+++ b/src/Happstack/Server/Internal/Types.hs
@@ -21,8 +21,8 @@
 
 
 import Control.Exception (Exception, SomeException)
-#if !MIN_VERSION_mtl(2,3,0)
-import Control.Monad.Error (Error(strMsg))
+#if !MIN_VERSION_transformers(0,6,0)
+import Control.Monad.Trans.Error (Error(strMsg))
 #endif
 import Control.Monad.Fail (MonadFail)
 import Control.Monad.Trans (MonadIO(liftIO))
@@ -248,7 +248,7 @@
 showRsValidator :: Maybe (Response -> IO Response) -> String
 showRsValidator = maybe "Nothing" (const "Just <function>")
 
-#if !MIN_VERSION_mtl(2,3,0)
+#if !MIN_VERSION_transformers(0,6,0)
 -- what should the status code be ?
 instance Error Response where
   strMsg str =
diff --git a/src/Happstack/Server/Monads.hs b/src/Happstack/Server/Monads.hs
--- a/src/Happstack/Server/Monads.hs
+++ b/src/Happstack/Server/Monads.hs
@@ -41,8 +41,8 @@
 
 import Control.Applicative               (Alternative, Applicative)
 import Control.Monad                     (MonadPlus(mzero))
-#if !MIN_VERSION_mtl(2,3,0)
-import Control.Monad.Error               (Error, ErrorT)
+#if !MIN_VERSION_transformers(0,6,0)
+import Control.Monad.Trans.Error         (Error, ErrorT)
 #endif
 import Control.Monad.Trans               (MonadIO(..),MonadTrans(lift))
 import Control.Monad.Trans.Except        (ExceptT)
@@ -73,7 +73,7 @@
 instance (Happstack m, Monoid w) => Happstack (Strict.WriterT   w   m)
 instance (Happstack m, Monoid w) => Happstack (Lazy.RWST      r w s m)
 instance (Happstack m, Monoid w) => Happstack (Strict.RWST    r w s m)
-#if !MIN_VERSION_mtl(2,3,0)
+#if !MIN_VERSION_transformers(0,6,0)
 instance (Happstack m, Error e)  => Happstack (ErrorT e m)
 #endif
 instance (Happstack m, Monoid e) => Happstack (ExceptT e m)
diff --git a/src/Happstack/Server/RqData.hs b/src/Happstack/Server/RqData.hs
--- a/src/Happstack/Server/RqData.hs
+++ b/src/Happstack/Server/RqData.hs
@@ -67,8 +67,8 @@
 import qualified Control.Monad.Writer.Strict as Strict (WriterT, mapWriterT)
 import qualified Control.Monad.RWS.Lazy as Lazy        (RWST, mapRWST)
 import qualified Control.Monad.RWS.Strict as Strict    (RWST, mapRWST)
-#if !MIN_VERSION_mtl(2,3,0)
-import qualified Control.Monad.Error as DeprecatedError
+#if !MIN_VERSION_transformers(0,6,0)
+import qualified Control.Monad.Trans.Error as DeprecatedError
 #endif
 import Control.Monad.Except                     (throwError)
 import Control.Monad.Trans                      (MonadIO(..), lift)
@@ -95,13 +95,13 @@
 newtype ReaderError r e a = ReaderError { unReaderError :: ReaderT r (Either e) a }
     deriving (Functor, Monad)
 
-#if MIN_VERSION_mtl(2,3,0)
+#if MIN_VERSION_transformers(0,6,0)
 deriving instance (Monoid e, MonadPlus (Either e)) => MonadPlus (ReaderError r e)
 #else
 deriving instance (Monoid e, DeprecatedError.Error e, MonadPlus (Either e)) => MonadPlus (ReaderError r e)
 #endif
 
-#if MIN_VERSION_mtl(2,3,0)
+#if MIN_VERSION_transformers(0,6,0)
 instance (Monoid e) => MonadReader r (ReaderError r e) where
 #else
 instance (DeprecatedError.Error e, Monoid e) => MonadReader r (ReaderError r e) where
@@ -109,7 +109,7 @@
     ask = ReaderError ask
     local f m = ReaderError $ local f (unReaderError m)
 
-#if MIN_VERSION_mtl(2,3,0)
+#if MIN_VERSION_transformers(0,6,0)
 instance (Monoid e) => Applicative (ReaderError r e) where
 #else
 instance (Monoid e, DeprecatedError.Error e) => Applicative (ReaderError r e) where
@@ -118,7 +118,7 @@
     (ReaderError (ReaderT f)) <*> (ReaderError (ReaderT a))
         = ReaderError $ ReaderT $ \env -> (f env) `apEither` (a env)
 
-#if MIN_VERSION_mtl(2,3,0)
+#if MIN_VERSION_transformers(0,6,0)
 instance (MonadPlus (Either e), Monoid e) => Alternative (ReaderError r e) where
 #else
 instance (Monoid e, DeprecatedError.Error e) => Alternative (ReaderError r e) where
@@ -156,7 +156,7 @@
   m        <|> _ = m
 #endif
 
-#if !MIN_VERSION_mtl(2,3,0)
+#if !MIN_VERSION_transformers(0,6,0)
 instance DeprecatedError.Error (Errors String) where
     noMsg = Errors []
     strMsg str = Errors [str]
@@ -242,7 +242,7 @@
     localRqEnv f  = Strict.mapRWST (localRqEnv f)
     rqDataError e = lift (rqDataError e)
 
-#if !MIN_VERSION_mtl(2,3,0)
+#if !MIN_VERSION_transformers(0,6,0)
 instance (Monad m, DeprecatedError.Error e, HasRqData m) => HasRqData (DeprecatedError.ErrorT e m) where
     askRqEnv      = lift askRqEnv
     localRqEnv f  = DeprecatedError.mapErrorT (localRqEnv f)
