diff --git a/CHANGES.rst b/CHANGES.rst
index 70bab91..e06cd02 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -2,6 +2,12 @@
 CHANGES
 =======
 
+4.2.1 (unreleased)
+------------------
+
+- TBD
+
+
 4.2.0 (2014-12-27)
 ------------------
 
diff --git a/setup.py b/setup.py
index 92f97ca..f2f206d 100644
--- a/setup.py
+++ b/setup.py
@@ -28,7 +28,7 @@ def read(*rnames):
         return f.read()
 
 setup(name='zope.error',
-    version='4.2.0',
+    version='4.2.1.dev0',
     author='Zope Foundation and Contributors',
     author_email='zope-dev@zope.org',
     description = "An error reporting utility for Zope3",