1 files changed, 3 insertions, 0 deletions
diff --git a/src/Map.hs b/src/Map.hs
index 8e59f83e..7d4c75df 100644
--- a/src/Map.hs
+++ b/src/Map.hs
@@ -18,6 +18,9 @@ import Data.FiniteMap
 
 type Map k a = FiniteMap k a
 
+instance Functor (FiniteMap k) where
+	fmap f = mapFM (const f)
+
 member :: Ord k => k -> Map k a -> Bool
 member = elemFM