--- shelly-1.5.2/src/Shelly/Pipe.hs~	2014-03-25 12:34:44.000000000 +0900
+++ shelly-1.5.2/src/Shelly/Pipe.hs	2016-10-05 16:54:59.613245757 +0900
@@ -138,6 +138,10 @@
     pure = return
     (<*>) = ap
 
+instance Alternative Sh where
+    (<|>) = mplus
+    empty = mzero
+
 instance MonadPlus Sh where
     mzero = Sh $ return []
     mplus a b = Sh $ liftA2 (++) (unSh a) (unSh b)