diff --git a/hasty-hamiltonian.cabal b/hasty-hamiltonian.cabal
--- a/hasty-hamiltonian.cabal
+++ b/hasty-hamiltonian.cabal
@@ -1,5 +1,5 @@
 name:                hasty-hamiltonian
-version:             1.3.3
+version:             1.3.4
 synopsis:            Speedy traversal through parameter space.
 homepage:            http://github.com/jtobin/hasty-hamiltonian
 license:             MIT
@@ -55,7 +55,7 @@
     , kan-extensions   >= 5 && < 6
     , mcmc-types       >= 1.0.1
     , mwc-probability  >= 2.0 && < 3
-    , lens             >= 4 && < 5
+    , lens             >= 4 && < 6
     , pipes            >= 4 && < 5
     , primitive        >= 0.5 && < 1.0
     , transformers     >= 0.5 && < 1.0