diff --git a/CHANGES.txt b/CHANGES.txt
index d1299f6..b40f02f 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -2,6 +2,12 @@
 CHANGES
 =======
 
+0.5.1dev (unreleased)
+---------------------
+
+- ...
+
+
 0.5.0 (2007-01-21)
 ------------------
 
diff --git a/setup.py b/setup.py
index 80dadd5..7cee85b 100644
--- a/setup.py
+++ b/setup.py
@@ -23,7 +23,7 @@ def read(*rnames):
 
 setup (
     name='z3c.json',
-    version='0.5.0',
+    version='0.5.1dev',
     author = "Roger Ineichen and the Zope Community",
     author_email = "zope3-dev@zope.org",
     description = "Zope3 JSON base libraries used for z3c.jsonpage and z3c.jsonrpc",