diff --git a/xcb-types.cabal b/xcb-types.cabal
--- a/xcb-types.cabal
+++ b/xcb-types.cabal
@@ -1,5 +1,5 @@
 Name:         xcb-types
-Version:      0.5.1
+Version:      0.5.1.1
 Cabal-Version:  >= 1.2
 Synopsis:     Parses XML files used by the XCB project
 Description:   This package provides types which mirror the structures
@@ -30,7 +30,7 @@
 
 Library
 
- Build-depends: base, xml, pretty, mtl
+ Build-depends: base, xml, pretty, mtl < 1.2
  Exposed-modules: Data.XCB,
                   Data.XCB.Types,
                   Data.XCB.Pretty,