diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,10 @@
 # Changelog for polysemy-check
 
+## v0.7.0.0 (2021-10-16)
+
+- Removed the `x` type variable from `prepropEquivalent`, since it is safe to
+    instantiate arbitrarily, and leads to aggressive type errors if forgotten.
+
 ## v0.6.0.0 (2021-10-16)
 
 - Changed the frequencies of `Sem`'s `Arbitrary` instance, to create more
diff --git a/polysemy-check.cabal b/polysemy-check.cabal
--- a/polysemy-check.cabal
+++ b/polysemy-check.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           polysemy-check
-version:        0.6.0.0
+version:        0.7.0.0
 synopsis:       QuickCheck for Polysemy
 description:    Please see the README on GitHub at <https://github.com/polysemy-research/polysemy-check#readme>
 category:       Polysemy
diff --git a/src/Polysemy/Check.hs b/src/Polysemy/Check.hs
--- a/src/Polysemy/Check.hs
+++ b/src/Polysemy/Check.hs
@@ -144,15 +144,13 @@
 -- | Prove that two interpreters are equivalent. This property ensures that the
 -- two interpreters give the same result for every arbitrary program.
 prepropEquivalent
-    :: forall effs x r1 r2 f
+    :: forall effs r1 r2 f
      . ( forall a. Show a => Show (f a)
        , forall a. Eq a => Eq (f a)
        )
-    => ( Eq x
-       , Show x
-       , Inject effs r1
+    => ( Inject effs r1
        , Inject effs r2
-       , Arbitrary (Sem effs x)
+       , Arbitrary (Sem effs Int)
        )
     => (forall a. Sem r1 a -> IO (f a))
        -- ^ The first interpreter for the effect stack.Pure effect stacks can
@@ -161,7 +159,7 @@
        -- ^ The second interpreter to prove equivalence for.
     -> Property
 prepropEquivalent int1 int2 = property $ do
-  SomeSem sem <- liftGen @effs @x
+  SomeSem sem <- liftGen @effs @Int
   pure $ ioProperty $ do
     a1 <- int1 sem
     a2 <- int2 sem
diff --git a/test/EquivSpec.hs b/test/EquivSpec.hs
--- a/test/EquivSpec.hs
+++ b/test/EquivSpec.hs
@@ -19,7 +19,7 @@
   prop "Pure state is equivalent to IO state" $ do
     s0 <- arbitrary
     pure $
-      prepropEquivalent @'[State Int] @Int
+      prepropEquivalent @'[State Int]
         (runPureState s0)
         (runIOState s0)
 
diff --git a/test/ExampleSpec.hs b/test/ExampleSpec.hs
--- a/test/ExampleSpec.hs
+++ b/test/ExampleSpec.hs
@@ -71,7 +71,7 @@
 
   describe "Equivalence" $ do
     let equiv b1 b2 =
-          prepropEquivalent @'[Stack Int] @Int
+          prepropEquivalent @'[Stack Int]
             (pure . run . runStack b1)
             (pure . run . runStack b2)