diff --git a/happstack-ixset.cabal b/happstack-ixset.cabal
--- a/happstack-ixset.cabal
+++ b/happstack-ixset.cabal
@@ -1,5 +1,5 @@
 Name:                happstack-ixset
-Version:             0.5.0.2
+Version:             0.5.0.3
 Synopsis:            Efficient relational queries on Haskell sets. 
 Description:         Just pick which parts of your data structures you want indexed using an easy to use template-haskell function. Spare yourself the need to write, run, and maintain code that marshalls your data to/from an external relational database just for efficient queries. happstack-ixset relies on generics and TH to spare you the boilerplate normally required for such tasks. 
 License:             BSD3
@@ -37,7 +37,7 @@
   Build-Depends:       containers,
                        happstack-data >= 0.5 && < 0.6,
                        happstack-util >= 0.5 && < 0.6,
-                       mtl,
+                       mtl >= 1.1 && < 2.1,
                        syb-with-class,
                        template-haskell