diff --git a/ListTree.cabal b/ListTree.cabal
--- a/ListTree.cabal
+++ b/ListTree.cabal
@@ -1,5 +1,5 @@
 Name:                ListTree
-Version:             0.2.1
+Version:             0.2.2
 Category:            Algorithms
 Synopsis:            Trees and monadic trees expressed as monadic lists where the underlying monad is a list
 Description:
diff --git a/src/Data/List/Tree.hs b/src/Data/List/Tree.hs
--- a/src/Data/List/Tree.hs
+++ b/src/Data/List/Tree.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE FlexibleContexts, FlexibleInstances, UndecidableInstances #-}
+{-# LANGUAGE FlexibleContexts, FlexibleInstances, TypeFamilies, UndecidableInstances #-}
 
 -- | Functions for iterating trees.
 -- A 'List' whose underlying monad is also a 'List' is a tree.