diff --git a/deque.cabal b/deque.cabal
--- a/deque.cabal
+++ b/deque.cabal
@@ -1,7 +1,7 @@
 name:
   deque
 version:
-  0.2.3
+  0.2.4
 synopsis:
   Double-ended queue
 description:
diff --git a/library/Deque.hs b/library/Deque.hs
--- a/library/Deque.hs
+++ b/library/Deque.hs
@@ -165,6 +165,8 @@
     pure
   m >>= f =
     fromList (toList m >>= toList . f)
+  fail =
+    const mempty
 
 instance Alternative Deque where
   empty =