diff --git a/daytripper.cabal b/daytripper.cabal
--- a/daytripper.cabal
+++ b/daytripper.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           daytripper
-version:        0.3.0
+version:        0.3.1
 synopsis:       Helpers for round-trip tests
 description:    Please see the README on GitHub at <https://github.com/ejconlon/daytripper#readme>
 homepage:       https://github.com/ejconlon/daytripper#readme
@@ -62,7 +62,7 @@
     , bytestring ==0.11.*
     , directory ==1.3.*
     , falsify ==0.2.*
-    , optparse-applicative ==0.17.*
+    , optparse-applicative >=0.17 && <0.19
     , tagged ==0.8.*
     , tasty ==1.4.*
     , tasty-hunit ==0.10.*
@@ -107,7 +107,7 @@
     , daytripper
     , directory ==1.3.*
     , falsify ==0.2.*
-    , optparse-applicative ==0.17.*
+    , optparse-applicative >=0.17 && <0.19
     , tagged ==0.8.*
     , tasty ==1.4.*
     , tasty-hunit ==0.10.*
diff --git a/src/Test/Daytripper.hs b/src/Test/Daytripper.hs
--- a/src/Test/Daytripper.hs
+++ b/src/Test/Daytripper.hs
@@ -38,7 +38,7 @@
 
 -- | Interface for asserting and performing IO in tests.
 -- TODO Migrate to 'MonadIO' superclass when Falsify supports it.
-class MonadFail m => MonadExpect m where
+class (MonadFail m) => MonadExpect m where
   expectLiftIO :: IO a -> m a
   expectAssertEq :: (Eq a, Show a) => a -> a -> m ()
   expectAssertFailure :: String -> m ()
@@ -66,21 +66,21 @@
 eitherMay = either (const Nothing) Just
 
 -- | Assert something before processing (before encoding and before decoding)
-expectBefore :: Monad m => (Maybe a -> m ()) -> Expect m a b c -> Expect m a b c
+expectBefore :: (Monad m) => (Maybe a -> m ()) -> Expect m a b c -> Expect m a b c
 expectBefore f ex i = f (eitherMay i) >> ex i
 
 -- | Assert something during processing (after encoding and before decoding)
-expectDuring :: Monad m => (Maybe a -> b -> m ()) -> Expect m a b c -> Expect m a b c
+expectDuring :: (Monad m) => (Maybe a -> b -> m ()) -> Expect m a b c -> Expect m a b c
 expectDuring f ex i = ex i >>= \p@(b, _) -> p <$ f (eitherMay i) b
 
 -- | Asserting something after processing (after encoding and after decoding)
-expectAfter :: Monad m => (Maybe a -> b -> c -> m ()) -> Expect m a b c -> Expect m a b c
+expectAfter :: (Monad m) => (Maybe a -> b -> c -> m ()) -> Expect m a b c -> Expect m a b c
 expectAfter f ex i = ex i >>= \(b, end) -> end >>= \c -> (b, pure c) <$ f (eitherMay i) b c
 
 -- | A way of definining expectations from a pair of encode/decode functions and
 -- a comparison function.
 mkExpect
-  :: MonadExpect m
+  :: (MonadExpect m)
   => (a -> m b)
   -> (b -> m c)
   -> (Maybe a -> c -> m ())
@@ -93,14 +93,14 @@
     pure c
 
 -- | Simple way to run an expectation, ignoring the intermediate value.
-runExpect :: Monad m => Expect m a b c -> a -> m c
+runExpect :: (Monad m) => Expect m a b c -> a -> m c
 runExpect f a = f (Right a) >>= snd
 
 data PropRT where
-  PropRT :: Show a => TestName -> Expect Property a b c -> Gen a -> PropRT
+  PropRT :: (Show a) => TestName -> Expect Property a b c -> Gen a -> PropRT
 
 -- | Create a property-based roundtrip test
-mkPropRT :: Show a => TestName -> Expect Property a b c -> Gen a -> RT
+mkPropRT :: (Show a) => TestName -> Expect Property a b c -> Gen a -> RT
 mkPropRT name expec gen = RTProp (PropRT name expec gen)
 
 testPropRT :: PropRT -> TestTree
diff --git a/test/Main.hs b/test/Main.hs
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -15,7 +15,7 @@
 
 type Cmp m = Maybe ByteString -> Maybe ByteString -> m ()
 
-expec :: MonadExpect m => Cmp m -> Expect m ByteString ByteString (Maybe ByteString)
+expec :: (MonadExpect m) => Cmp m -> Expect m ByteString ByteString (Maybe ByteString)
 expec = mkExpect enc dec
  where
   enc a = pure (a <> a)
@@ -26,7 +26,7 @@
             then Just a
             else Nothing
 
-expecOk, expecFail :: MonadExpect m => Expect m ByteString ByteString (Maybe ByteString)
+expecOk, expecFail :: (MonadExpect m) => Expect m ByteString ByteString (Maybe ByteString)
 expecOk =
   expec $
     maybe