diff --git a/safe-freeze.cabal b/safe-freeze.cabal
--- a/safe-freeze.cabal
+++ b/safe-freeze.cabal
@@ -1,5 +1,5 @@
 Name:          safe-freeze
-Version:       0.2
+Version:       0.2.1
 Synopsis:      Support for safely freezing multiple arrays in the ST monad.
 License:       BSD3
 License-file:  LICENSE
@@ -43,5 +43,5 @@
   Build-Depends:   
     base< 5, 
     indexed < 0.2,
-    mtl == 2.0.*,
+    mtl >= 2.0 && < 2.2,
     vector>=0.4 && < 0.10