diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5ca46c8..361477f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -124,9 +124,9 @@ jobs:
           name: ${{ matrix.os }}-${{ matrix.ghc }}-plan.json
           path: mtl-*/dist-newstyle/cache/plan.json
 
-#       - name: Test
-#         run: |
-#           cabal --enable-tests --test-show-details=direct all
+      - name: Test
+        run: |
+          cabal test
 
       - name: Haddock
         run: |
@@ -166,12 +166,16 @@ jobs:
           # build
           stack build
 
+      - name: Test
+        run: |
+          stack test
+
   mhs:
     name: "MicroHS ${{ matrix.mhs }}"
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        mhs: ["0.15.4.0"]
+        mhs: ["0.16.0.0"]
       fail-fast: false
     steps:
       - name: checkout mhs repo
@@ -196,3 +200,8 @@ jobs:
         run: |
           cd mtl
           mcabal -r install
+
+      - name: test
+        run: |
+          cd mtl
+          mcabal test
diff --git a/.gitignore b/.gitignore
index 55a715d..bcca8b0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 dist
 dist-boot
 dist-install
+dist-mcabal
 dist-newstyle
 ghc.mk
 GNUmakefile
@@ -20,6 +21,7 @@ cabal.sandbox.config
 *.hp
 *.eventlog
 .stack-work/
+stack.yaml*
 cabal.project.local*
 .HTF/
 .ghc.environment.*
diff --git a/Control/Monad/Cont/Class.hs b/Control/Monad/Cont/Class.hs
index 6bc4d78..9d85be6 100644
--- a/Control/Monad/Cont/Class.hs
+++ b/Control/Monad/Cont/Class.hs
@@ -114,12 +114,7 @@ class Monad m => MonadCont (m :: Type -> Type) where
     {-# MINIMAL callCC #-}
 
 -- | @since 2.3.1
-#ifdef __MHS__
--- The ContT type is not polykinded with mhs.
 instance MonadCont (ContT r m) where
-#else
-instance forall k (r :: k) (m :: (k -> Type)) . MonadCont (ContT r m) where
-#endif
     callCC = ContT.callCC
 
 -- ---------------------------------------------------------------------------
diff --git a/mtl.cabal b/mtl.cabal
index 0fcd9d3..1d19a37 100644
--- a/mtl.cabal
+++ b/mtl.cabal
@@ -24,7 +24,9 @@ extra-source-files:
 extra-doc-files:
   CHANGELOG.markdown
 
-tested-with: GHC ==8.10 || ==9.2 || ==9.8 || ==9.10 || ==9.12, MHS ==0.14.15.0
+tested-with:
+  , GHC ==8.10 || ==9.2 || ==9.8 || ==9.10 || ==9.12 || ==9.14
+  , MHS ==0.16.0.0
 
 source-repository head
   type: git
@@ -67,3 +69,10 @@ Library
     -Wmissing-export-lists
 
   default-language: Haskell2010
+
+test-suite MonadCont
+  type: exitcode-stdio-1.0
+  hs-source-dirs: test
+  main-is: MonadCont.hs
+  default-language: Haskell2010
+  build-depends: base, mtl, transformers
diff --git a/test/MonadCont.hs b/test/MonadCont.hs
new file mode 100644
index 0000000..c657ab8
--- /dev/null
+++ b/test/MonadCont.hs
@@ -0,0 +1,19 @@
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE DataKinds #-}
+
+{-# OPTIONS_GHC -Wno-unused-binds #-}
+
+module Main (main) where
+
+import Control.Monad.Trans.Cont (ContT)
+import Control.Monad.Cont.Class (MonadCont (callCC))
+import Data.Proxy (Proxy)
+
+#ifdef __GLASGOW_HASKELL__
+-- Test that MonadCont is possible with polykinded ContT
+x :: (ContT 42 Proxy) ()
+x = callCC $ \_ -> return ()
+#endif
+
+main :: IO ()
+main = return ()