diff --git a/src/Control/Monad/Stream.hs b/src/Control/Monad/Stream.hs
index fd7cd31..3081a47 100644
--- a/src/Control/Monad/Stream.hs
+++ b/src/Control/Monad/Stream.hs
@@ -69,6 +69,8 @@ instance Monad Stream
   Cons x xs >>= f = f x `mplus` suspended (xs >>= f)
   Susp xs   >>= f = suspended (xs >>= f)
 
+instance MonadFail Stream
+ where
   fail _ = Nil
 
 instance MonadPlus Stream