diff --git a/CHANGES.rst b/CHANGES.rst
index 86ea65e..0bbdd3f 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,6 +1,12 @@
 Changes
 =======
 
+4.2.1 (unreleased)
+------------------
+
+- Nothing changed yet.
+
+
 4.2.0 (2017-07-25)
 ------------------
 
diff --git a/setup.py b/setup.py
index 5633bfd..48ceec9 100644
--- a/setup.py
+++ b/setup.py
@@ -54,7 +54,7 @@ def alltests():
 
 setup(
     name="zope.dublincore",
-    version='4.2.0',
+    version='4.2.1.dev0',
     url='http://github.com/zopefoundation/zope.dublincore',
     license='ZPL 2.1',
     description='Zope Dublin Core implementation',