commit 8d867a693f91406f9b45e24d79a0637013c0e272
Author: Ollie Charles <ollie@ocharles.org.uk>
Date:   Wed Sep 18 14:48:23 2019 +0100

    Update Pure.hs

diff --git a/src/Codec/Crypto/RSA/Pure.hs b/src/Codec/Crypto/RSA/Pure.hs
index 8e0f483..a69907d 100644
--- a/src/Codec/Crypto/RSA/Pure.hs
+++ b/src/Codec/Crypto/RSA/Pure.hs
@@ -111,7 +111,7 @@ instance Binary PrivateKey where
               d   <- os2ip `fmap` getLazyByteString (fromIntegral (public_size pub))
               return (PrivateKey pub d 0 0 0 0 0)
 
-failOnError :: (Monad m, Show a) => Either a b -> m b
+failOnError :: (MonadFail m, Show a) => Either a b -> m b
 failOnError (Left e)  = fail (show e)
 failOnError (Right b) = return b