diff --git a/mcmc-types.cabal b/mcmc-types.cabal
--- a/mcmc-types.cabal
+++ b/mcmc-types.cabal
@@ -1,5 +1,5 @@
 name:                mcmc-types
-version:             1.0.2
+version:             1.0.3
 synopsis:            Common types for sampling.
 homepage:            http://github.com/jtobin/mcmc-types
 license:             MIT
@@ -34,5 +34,5 @@
       base            >= 4 && < 6
     , containers      >= 0.5 && < 6
     , mwc-probability >= 1.0.1
-    , transformers
+    , transformers    >= 0.5 && < 1.0