diff --git a/library/Success/Impure.hs b/library/Success/Impure.hs
--- a/library/Success/Impure.hs
+++ b/library/Success/Impure.hs
@@ -49,7 +49,7 @@
           Left (Just e) -> pure (Success.Pure.failure e)
           Right x -> run (m2' x)
 
-instance Monad m => MonadPlus (Success e m) where
+instance (Applicative m, Monad m) => MonadPlus (Success e m) where
   {-# INLINE mzero #-}
   mzero =
     empty
diff --git a/success.cabal b/success.cabal
--- a/success.cabal
+++ b/success.cabal
@@ -1,7 +1,7 @@
 name:
   success
 version:
-  0.2
+  0.2.1
 synopsis:
   A version of Either specialised for encoding of success or failure
 description: