diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,8 @@
+# Version 0.5.1
+
+* Bump upper bound dependency on `attoparsec`.
+
+
 # Version 0.5.0
 
 * Correctly propagate state in `parsedL`.
diff --git a/pipes-attoparsec.cabal b/pipes-attoparsec.cabal
--- a/pipes-attoparsec.cabal
+++ b/pipes-attoparsec.cabal
@@ -1,5 +1,5 @@
 name:               pipes-attoparsec
-version:            0.5.0
+version:            0.5.1
 license:            BSD3
 license-file:       LICENSE
 copyright:          Copyright (c) Renzo Carbonara 2012-2014, Paolo Capriotti 2012
@@ -28,12 +28,12 @@
   exposed-modules: Pipes.Attoparsec
   build-depends:
       base         (>=4.5      && <5.0)
-    , attoparsec   (>=0.10     && <0.12)
+    , attoparsec   (>=0.10     && <0.13)
     , bytestring   (>=0.9.2.1  && <0.11)
     , pipes        (>=4.1      && <4.2)
     , pipes-parse  (>=3.0.1    && <3.1)
     , text         (>=0.11.2.0 && <1.2)
-    , transformers (>=0.2      && <0.4)
+    , transformers (>=0.2      && <0.5)
   ghc-options: -Wall -O2
 
 test-suite tests