diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
+4.3.4
+
+* Increase upper bound on `mmorph`
+
 4.3.3
-    * Make `X` a synonym for `Data.Void.Void`
+
+* Make `X` a synonym for `Data.Void.Void`
 
 4.3.2
 
diff --git a/pipes.cabal b/pipes.cabal
--- a/pipes.cabal
+++ b/pipes.cabal
@@ -1,5 +1,5 @@
 Name: pipes
-Version: 4.3.3
+Version: 4.3.4
 Cabal-Version: >= 1.10
 Build-Type: Simple
 Tested-With: GHC == 7.4.2, GHC == 7.6.3, GHC == 7.8.4, GHC == 7.10.2, GHC == 8.0.1
@@ -49,7 +49,7 @@
         base         >= 4.4     && < 5  ,
         transformers >= 0.2.0.0 && < 0.6,
         exceptions   >= 0.4     && < 0.9,
-        mmorph       >= 1.0.0   && < 1.1,
+        mmorph       >= 1.0.0   && < 1.2,
         mtl          >= 2.2.1   && < 2.3,
         void         >= 0.4     && < 0.8