diff --git a/chatty.cabal b/chatty.cabal
--- a/chatty.cabal
+++ b/chatty.cabal
@@ -10,7 +10,7 @@
 -- PVP summary:      +-+------- breaking API changes
 --                   | | +----- non-breaking API additions
 --                   | | | +--- code changes with no API change
-version:             0.5.1.0
+version:             0.5.1.1
 
 -- A short (one-line) description of the package.
 synopsis:            Some monad transformers and typeclasses to simplify I/O on a transformer stack.
@@ -54,7 +54,7 @@
   -- other-modules:       
   
   -- LANGUAGE extensions used by modules in this package.
-  other-extensions:    ExistentialQuantification, RankNTypes, Rank2Types, FlexibleInstances, MultiParamTypeClasses, FunctionalDependencies, TemplateHaskell, QuasiQuotes
+  other-extensions:    ExistentialQuantification, RankNTypes, Rank2Types, FlexibleInstances, MultiParamTypeClasses, FunctionalDependencies, TemplateHaskell, QuasiQuotes, UndecidableInstances
   
   -- Other library packages from which modules are imported.
   build-depends:       base >=4.6 && <4.7, transformers >=0.3 && <0.4, directory >=1.2 && <1.3, process >=1.1 && <1.2, mtl >=2.1 && <2.2, template-haskell >=2.8 && <2.9, setenv >= 0.1 && <0.2, unix >= 2.6 && < 2.7, random >= 1.0 && < 1.1, time >= 1.4 && < 1.5, ansi-terminal >= 0.6 && <0.7