diff --git a/happstack-util.cabal b/happstack-util.cabal
--- a/happstack-util.cabal
+++ b/happstack-util.cabal
@@ -1,5 +1,5 @@
 Name:                happstack-util
-Version:             0.5.0.2
+Version:             0.5.0.3
 Synopsis:            Web framework
 License:             BSD3
 License-file:        COPYING
@@ -29,7 +29,7 @@
                        directory,
                        extensible-exceptions, 
                        hslogger >= 1.0.2,
-                       mtl,
+                       mtl >= 1.1 && < 2.1,
                        old-locale,
                        old-time,
                        parsec < 4,