diff --git a/cabal.project b/cabal.project
index 1671440..5c0072e 100644
--- a/cabal.project
+++ b/cabal.project
@@ -1,2 +1,9 @@
 packages:
   .
+-- Always write GHC env files, because they are needed for repl and by the doctests.
+write-ghc-environment-files: always
+-- Always build tests and benchmarks.
+tests: true
+benchmarks: true
+-- The only sensible test display option
+test-show-details: streaming
diff --git a/constrained-generators.cabal b/constrained-generators.cabal
index a271f63..1b487af 100644
--- a/constrained-generators.cabal
+++ b/constrained-generators.cabal
@@ -79,7 +79,7 @@ library
     -Wunused-packages
 
   build-depends:
-    QuickCheck >=2.14,
+    QuickCheck >=2.14 && <2.18,
     base >=4.18 && <5,
     base-orphans,
     containers,
diff --git a/src/Constrained/Core.hs b/src/Constrained/Core.hs
index 95714e3..e4e14e3 100644
--- a/src/Constrained/Core.hs
+++ b/src/Constrained/Core.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE ImportQualifiedPost #-}
@@ -35,11 +36,15 @@ import Constrained.PrettyUtils
 import Control.Applicative
 import Data.Function
 import Data.List.NonEmpty (NonEmpty ((:|)))
-import Data.List.NonEmpty qualified as NE
 import Data.Set (Set)
 import Data.Set qualified as Set
 import Data.Typeable
+
+-- Orphan instance for old QuickCheck versions
+#if !MIN_VERSION_QuickCheck(2, 17, 0)
+import Data.List.NonEmpty qualified as NE
 import Test.QuickCheck (Arbitrary (..), NonEmptyList (NonEmpty))
+#endif
 
 -- Variables --------------------------------------------------------------
 
@@ -135,7 +140,9 @@ instance Typeable c => Show (Evidence c) where
 unionWithMaybe :: (a -> a -> a) -> Maybe a -> Maybe a -> Maybe a
 unionWithMaybe f ma ma' = (f <$> ma <*> ma') <|> ma <|> ma'
 
+#if !MIN_VERSION_QuickCheck(2, 17, 0)
 instance Arbitrary a => Arbitrary (NonEmpty a) where
   arbitrary = do
     NonEmpty xs <- arbitrary
     pure (NE.fromList xs)
+#endif
diff --git a/src/Constrained/NumOrd.hs b/src/Constrained/NumOrd.hs
index cccd3f2..df4027a 100644
--- a/src/Constrained/NumOrd.hs
+++ b/src/Constrained/NumOrd.hs
@@ -1,5 +1,6 @@
 {-# LANGUAGE AllowAmbiguousTypes #-}
 {-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE DefaultSignatures #-}
 {-# LANGUAGE DerivingVia #-}
@@ -257,9 +258,11 @@ instance (Arbitrary a, Ord a) => Arbitrary (NumSpec a) where
   shrink (NumSpecInterval m m') =
     uncurry NumSpecInterval <$> shrink (m, m')
 
+#if !MIN_VERSION_QuickCheck(2, 17, 0)
 instance Arbitrary Natural where
   arbitrary = wordToNatural . abs <$> arbitrary
   shrink n = [wordToNatural w | w <- shrink (naturalToWord n)]
+#endif
 
 instance Uniform Natural where
   uniformM g = wordToNatural . abs <$> uniformM g