diff --git a/hoauth2.cabal b/hoauth2.cabal
--- a/hoauth2.cabal
+++ b/hoauth2.cabal
@@ -2,11 +2,9 @@
 name:               hoauth2
 
 -- http://wiki.haskell.org/Package_versioning_policy
-version:            2.8.0
+version:            2.8.1
 synopsis:           Haskell OAuth2 authentication client
-description:
-  See readme for more details.
-
+description:        See readme for more details.
 homepage:           https://github.com/freizl/hoauth2
 license:            MIT
 license-file:       LICENSE
@@ -16,7 +14,7 @@
 category:           Network
 build-type:         Simple
 stability:          Beta
-tested-with:        GHC <=9.2.2
+tested-with:        GHC <=9.6.1
 extra-source-files: README.org
 
 source-repository head
@@ -66,7 +64,7 @@
     , memory                ^>=0.18
     , microlens             ^>=0.4.0
     , text                  ^>=2.0
-    , transformers          ^>=0.5
+    , transformers          >=0.6
     , uri-bytestring        >=0.2.3  && <0.4
     , uri-bytestring-aeson  ^>=0.1
 
diff --git a/src/Network/OAuth2/Experiment/Types.hs b/src/Network/OAuth2/Experiment/Types.hs
--- a/src/Network/OAuth2/Experiment/Types.hs
+++ b/src/Network/OAuth2/Experiment/Types.hs
@@ -81,8 +81,6 @@
 
 -------------------------------------------------------------------------------
 
-newtype UrnOAuthParam a = UrnOAuthParam a
-
 -- | Grant type query parameter has association with 'GrantTypeFlow' but not completely strict.
 --
 -- e.g. Both 'AuthorizationCode' and 'ResourceOwnerPassword' flow could support refresh token flow.