diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,7 @@
+## 1.6.0.1
+
+* Compile with GHC 8.6 [#1561](https://github.com/yesodweb/yesod/pull/1561)
+
 ## 1.6.0
 
 * Upgrade to yesod-core 1.6.0
diff --git a/Yesod/Auth/OAuth.hs b/Yesod/Auth/OAuth.hs
--- a/Yesod/Auth/OAuth.hs
+++ b/Yesod/Auth/OAuth.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE DeriveDataTypeable, OverloadedStrings, QuasiQuotes #-}
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE ScopedTypeVariables #-}
@@ -69,7 +70,9 @@
         setSession oauthSessionName $ lookupTokenSecret tok
         redirect $ authorizeUrl oauth' tok
     dispatch "GET" [] = do
-      Just tokSec <- lookupSession oauthSessionName
+      tokSec <- lookupSession oauthSessionName >>= \case
+        Just t -> return t
+        Nothing -> liftIO $ fail "lookupSession could not find session"
       deleteSession oauthSessionName
       reqTok <-
         if oauthVersion oauth == OAuth10
diff --git a/yesod-auth-oauth.cabal b/yesod-auth-oauth.cabal
--- a/yesod-auth-oauth.cabal
+++ b/yesod-auth-oauth.cabal
@@ -1,5 +1,5 @@
 name:            yesod-auth-oauth
-version:         1.6.0
+version:         1.6.0.1
 license:         BSD3
 license-file:    LICENSE
 author:          Hiromi Ishii
@@ -23,12 +23,11 @@
         build-depends:   base                >= 4         && < 4.3
     build-depends:   authenticate-oauth      >= 1.5       && < 1.7
                    , bytestring              >= 0.9.1.4
-                   , yesod-core              >= 1.6       && < 1.7
-                   , yesod-auth              >= 1.6       && < 1.7
                    , text                    >= 0.7
-                   , yesod-form              >= 1.6       && < 1.7
-                   , transformers            >= 0.2.2     && < 0.6
                    , unliftio
+                   , yesod-auth              >= 1.6       && < 1.7
+                   , yesod-core              >= 1.6       && < 1.7
+                   , yesod-form              >= 1.6       && < 1.7
     exposed-modules: Yesod.Auth.OAuth
     ghc-options:     -Wall