diff --git a/README.md b/README.md
index 2700980..9409bf2 100644
--- a/README.md
+++ b/README.md
@@ -54,7 +54,7 @@ and the tests run using:
 ./mafia test
 ```
 
-Grenade is currently known to build with ghc 7.10. We are working on making it build with ghc 8.0.
+Grenade is currently known to build with ghc 7.10 and 8.0.
 
 
 Thanks
diff --git a/grenade.cabal b/grenade.cabal
index 44a5977..f160e8e 100644
--- a/grenade.cabal
+++ b/grenade.cabal
@@ -97,5 +97,5 @@ test-suite test
                      , hmatrix
                      , mtl
                      , text                            == 1.2.*
-                     , QuickCheck                      == 2.7.*
+                     , QuickCheck                      >= 2.7        && < 2.9
                      , quickcheck-instances            == 0.3.*
diff --git a/mafia b/mafia
index 3a9f823..0e2103f 100755
--- a/mafia
+++ b/mafia
@@ -118,4 +118,4 @@ case "$MODE" in
 upgrade) shift; run_upgrade "$@" ;;
 *) exec_mafia "$@"
 esac
-# Version: dbbe635d8f98be1815130f04465c155f414985bf
+# Version: a1b39ee8ac1969ed2e891b9062d079be75863e99
diff --git a/src/Grenade/Core/Runner.hs b/src/Grenade/Core/Runner.hs
index 6c5ee60..b3d841f 100644
--- a/src/Grenade/Core/Runner.hs
+++ b/src/Grenade/Core/Runner.hs
@@ -25,7 +25,7 @@ train :: forall m i o hs. (Monad m, Head hs ~ i, Last hs ~ o, KnownShape i, Know
       -> m (Network m hs)
 train rate x0 target = fmap fst . go x0
   where
-    go  :: forall m' j js. (Monad m', Head js ~ j, Last js ~ o, KnownShape j, KnownShape o)
+    go  :: forall m' j js. (Monad m', Head js ~ j, Last js ~ o, KnownShape j)
         => S' j                -- ^ input vector
         -> Network m' js       -- ^ network to train
         -> m' (Network m' js, S' j)
diff --git a/src/Grenade/Core/Shape.hs b/src/Grenade/Core/Shape.hs
index 0e90af5..a477cf2 100644
--- a/src/Grenade/Core/Shape.hs
+++ b/src/Grenade/Core/Shape.hs
@@ -11,6 +11,10 @@
 {-# LANGUAGE FlexibleContexts      #-}
 {-# LANGUAGE FlexibleInstances     #-}
 
+-- Ghc 8.0 gives a warning on `(+)  _ _ = error ...` but ghc 7.10 fails to
+-- compile without this default pattern.
+{-# OPTIONS_GHC -fno-warn-overlapping-patterns #-}
+
 module Grenade.Core.Shape (
     Shape (..)
   , S' (..)