1 files changed, 7 insertions, 1 deletions

diff --git a/lib/CommandLine.hs b/lib/CommandLine.hs
index dfc16f9..88584ce 100644
--- a/lib/CommandLine.hs
+++ b/lib/CommandLine.hs
@@ -65,7 +65,13 @@ data Expr a where
     --   Alternative empty
     Empty :: Expr a
 
-deriving instance Functor Expr
+-- deriving instance Functor Expr -- doesn't work on ghc 7.6.3
+instance Functor Expr where
+    fmap f (Prim g i) = Prim (\os us -> f $ g os us) i
+    fmap f (Star m a b) = Star m (fmap (f .) a) b
+    fmap f (Or m a b) = Or m (fmap f a) (fmap f b)
+    fmap f Empty = Empty
+
 
 -- | Args
 --