diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,12 @@
 # Changelog for polysemy-mocks
 
+## 0.3.0.0
+
+* Support template-haskell-2.17.0 (and so GHC 9.0)
+* Add 'HasCallStack' constraint to 'evalMocks', {run,eval,exec}Mock and default
+  implementations for the "returns" functions (which throws error, by default).
+  'RankNTypes' is now needed to use the TH mocks.
+
 ## 0.2.0.0
 
 * Support polysemy >= 1.7, drop support for older versions
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -13,6 +13,7 @@
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TemplateHaskell #-}
 {-# LANGUAGE TypeApplications #-}
diff --git a/polysemy-mocks.cabal b/polysemy-mocks.cabal
--- a/polysemy-mocks.cabal
+++ b/polysemy-mocks.cabal
@@ -1,7 +1,7 @@
 cabal-version: 1.12
 
 name:           polysemy-mocks
-version:        0.2.0.0
+version:        0.3.0.0
 description:    Please see the README on GitHub at <https://github.com/akshaymankar/polysemy-mocks#readme>
 homepage:       https://github.com/akshaymankar/polysemy-mocks#readme
 bug-reports:    https://github.com/akshaymankar/polysemy-mocks/issues
diff --git a/src/Test/Polysemy/Mock.hs b/src/Test/Polysemy/Mock.hs
--- a/src/Test/Polysemy/Mock.hs
+++ b/src/Test/Polysemy/Mock.hs
@@ -25,6 +25,7 @@
 where
 
 import Data.Kind
+import GHC.Stack (HasCallStack)
 import Polysemy
 import Polysemy.State
 
@@ -139,18 +140,18 @@
   -- | Interpret all actions of 'MockImpl eff m' to get 'State (MockImpl eff
   -- m)'. The 'State' effect could then be resolved using 'initialMockState'.
   -- Use 'runMock', 'evalMock' or 'execMock' for convinience.
-  mockToState :: Member (Embed m) r => Sem (MockImpl eff m ': r) a -> Sem (State (MockState eff m) ': r) a
+  mockToState :: (Member (Embed m) r, HasCallStack) => Sem (MockImpl eff m ': r) a -> Sem (State (MockState eff m) ': r) a
 
 -- | Run a mocked effect to get 'MockState' and the effect value
-runMock :: (Mock eff m, Member (Embed m) r) => Sem (MockImpl eff m ': r) a -> Sem r (MockState eff m, a)
+runMock :: (Mock eff m, Member (Embed m) r, HasCallStack) => Sem (MockImpl eff m ': r) a -> Sem r (MockState eff m, a)
 runMock = runState initialMockState . mockToState
 
 -- | Like 'runMock' but discards the 'MockState'
-evalMock :: (Mock eff m, Member (Embed m) r) => Sem (MockImpl eff m ': r) a -> Sem r a
+evalMock :: (Mock eff m, Member (Embed m) r, HasCallStack) => Sem (MockImpl eff m ': r) a -> Sem r a
 evalMock = evalState initialMockState . mockToState
 
 -- | Like 'runMock' but only returns the 'MockState'
-execMock :: (Mock eff m, Member (Embed m) r) => Sem (MockImpl eff m ': r) a -> Sem r (MockState eff m)
+execMock :: (Mock eff m, Member (Embed m) r, HasCallStack) => Sem (MockImpl eff m ': r) a -> Sem r (MockState eff m)
 execMock = execState initialMockState . mockToState
 
 -- | Mock many effects
@@ -159,7 +160,7 @@
   mockMany :: MockChain effs m r => Sem (effs :++: r) a -> Sem r a
 
   -- | Given a computation using Mock effects, evaluate the computation
-  evalMocks :: (MocksExist effs m, Member (Embed m) r) => Sem (MockImpls effs m :++: r) a -> Sem r a
+  evalMocks :: (MocksExist effs m, Member (Embed m) r, HasCallStack) => Sem (MockImpls effs m :++: r) a -> Sem r a
 
 instance MockMany '[] r m where
   mockMany = id
diff --git a/src/Test/Polysemy/Mock/TH.hs b/src/Test/Polysemy/Mock/TH.hs
--- a/src/Test/Polysemy/Mock/TH.hs
+++ b/src/Test/Polysemy/Mock/TH.hs
@@ -5,6 +5,7 @@
 
 import Data.Bifunctor (first)
 import Data.List (foldl')
+import GHC.Stack (HasCallStack)
 import Language.Haskell.TH hiding (Strict)
 import Polysemy (Embed, Members, Sem, interpret, pureT, reinterpretH)
 import Polysemy.Internal (embed, send)
@@ -116,6 +117,13 @@
       body = NormalB (AppE (AppTypeE sendFn t) theMock)
    in Match pat body []
 
+#if MIN_VERSION_template_haskell(2,17,0)
+#define UNQUALIFIED_DO Nothing
+#else
+#define UNQUALIFIED_DO
+#endif
+
+{- ORMOLU_DISABLE -}
 mkMockToStateMatch :: Type -> ConLiftInfo -> Match
 mkMockToStateMatch t c =
   let pat = ConP (mockConName c) (map VarP vars)
@@ -139,12 +147,14 @@
       body =
         NormalB
           ( DoE
+              UNQUALIFIED_DO
               [ getState t,
                 putState newState,
                 returnAsPureT
               ]
           )
    in Match pat body []
+{- ORMOLU_ENABLE -}
 
 mkReturnsToStateMatch :: Type -> ConLiftInfo -> Match
 mkReturnsToStateMatch t c =
@@ -155,6 +165,7 @@
       body =
         NormalB
           ( DoE
+              UNQUALIFIED_DO
               [ getState t,
                 putState newState,
                 returnNothing
@@ -169,6 +180,7 @@
       body =
         NormalB
           ( DoE
+              UNQUALIFIED_DO
               [ getState t,
                 returnCalls
               ]
@@ -183,15 +195,22 @@
   [Dec]
 mkReturnsSem mockImplEffType c =
   let funcName = mkName ("mock" <> nameBase (cliConName c) <> "Returns")
-      body = NormalB (InfixE (Just $ VarE 'send) (VarE '(.)) (Just $ ConE (returnsConName c)))
+      f = mkName "f"
+      body = NormalB $ VarE 'send `AppE` (ConE (returnsConName c) `AppE` VarE f)
       appArrowT = AppT . AppT ArrowT
       r = VarT $ mkName "r"
       semr t = ConT ''Sem `AppT` r `AppT` t
       typ = ForallT [] [membersEffListType mockImplEffType r] (returnsFunctionType c `appArrowT` semr (TupleT 0))
    in [ SigD funcName typ,
-        FunD funcName [Clause [] body []]
+        FunD funcName [Clause [VarP f] body []]
       ]
 
+#if MIN_VERSION_template_haskell(2,17,0)
+#define TY_VAR_SPECIFICTY SpecifiedSpec
+#else
+#define TY_VAR_SPECIFICTY
+#endif
+
 mkCallsSem ::
   -- | Should look like: @MockImpl Teletype n@
   -- n is assumed to be 'stateEffectName', maybe this is problematic, but it works for now
@@ -204,7 +223,11 @@
       body = NormalB $ typeAppliedSend `AppE` ConE (callsConName c)
       r = VarT $ mkName "r"
       semr t = ConT ''Sem `AppT` r `AppT` t
-      typ = ForallT [PlainTV returnsEffectName, PlainTV $ mkName "r"] [membersEffListType mockImplEffType r] (semr $ functionCallType c)
+      typ =
+        ForallT
+          [PlainTV returnsEffectName TY_VAR_SPECIFICTY, PlainTV (mkName "r") TY_VAR_SPECIFICTY]
+          [membersEffListType mockImplEffType r]
+          (semr $ functionCallType c)
    in [ SigD funcName typ,
         FunD funcName [Clause [] body []]
       ]
@@ -254,7 +277,7 @@
 returnsFunctionType c =
   let argTypes = (map snd $ cliFunArgs c)
       returnType = (AppT returnsEffect $ cliEffRes c)
-   in foldr (AppT . AppT ArrowT) returnType argTypes
+   in ForallT [] [ConT ''HasCallStack] $ foldr (AppT . AppT ArrowT) returnType argTypes
 
 returnsEffect :: Type
 returnsEffect = VarT returnsEffectName
diff --git a/test/Test/Polysemy/Mock/TeletypeTHSpec.hs b/test/Test/Polysemy/Mock/TeletypeTHSpec.hs
--- a/test/Test/Polysemy/Mock/TeletypeTHSpec.hs
+++ b/test/Test/Polysemy/Mock/TeletypeTHSpec.hs
@@ -5,6 +5,7 @@
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TemplateHaskell #-}
 {-# LANGUAGE TypeApplications #-}