diff --git a/constrained-generators.cabal b/constrained-generators.cabal
index 36b8d19..38af28d 100644
--- a/constrained-generators.cabal
+++ b/constrained-generators.cabal
@@ -138,6 +138,8 @@ test-suite constrained-tests
     -Wredundant-constraints
     -Wunused-packages
     -rtsopts
+    -threaded
+    -with-rtsopts=-N
 
   build-depends:
     QuickCheck >= 2.15.0.1,
diff --git a/test/Constrained/GraphSpec.hs b/test/Constrained/GraphSpec.hs
index efd236a..67abe3c 100644
--- a/test/Constrained/GraphSpec.hs
+++ b/test/Constrained/GraphSpec.hs
@@ -110,4 +110,4 @@ return []
 
 tests :: Bool -> Spec
 tests _nightly =
-  describe "Graph tests" $ sequence_ [ prop n (checkCoverage $ withMaxSuccess 1000 p) | (n, p) <- $allProperties ]
+  describe "Graph tests" $ parallel $ sequence_ [ prop n (checkCoverage $ withMaxSuccess 1000 p) | (n, p) <- $allProperties ]
diff --git a/test/Constrained/Tests.hs b/test/Constrained/Tests.hs
index 2351c96..fce7063 100644
--- a/test/Constrained/Tests.hs
+++ b/test/Constrained/Tests.hs
@@ -58,7 +58,7 @@ testAll :: IO ()
 testAll = hspec $ tests False
 
 tests :: Bool -> Spec
-tests nightly =
+tests nightly = parallel $
   describe "constrained" . modifyMaxSuccess (\ms -> if nightly then ms * 10 else ms) $ do
     testSpec "signumPositive" signumPositive
     testSpec "setOfPairLetSpec" setOfPairLetSpec
diff --git a/test/Tests.hs b/test/Tests.hs
index beecbcf..a988286 100644
--- a/test/Tests.hs
+++ b/test/Tests.hs
@@ -9,6 +9,6 @@ import Test.Hspec
 main :: IO ()
 main = do
   nightly <- isJust <$> lookupEnv "NIGHTLY"
-  hspec $ do
+  hspec $ parallel $ do
     Tests.tests nightly
     Graph.tests nightly