diff --git a/CHANGES.rst b/CHANGES.rst
index 6dc5f6e..f15e8cf 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -2,6 +2,12 @@
  Changes
 =========
 
+4.3 (unreleased)
+================
+
+- Nothing changed yet.
+
+
 4.2 (2018-10-10)
 ================
 
diff --git a/setup.py b/setup.py
index 9102477..06bdc32 100644
--- a/setup.py
+++ b/setup.py
@@ -51,7 +51,7 @@ def read(*rnames):
 )
 
 setup(name='zope.sendmail',
-      version='4.2',
+      version='4.3.dev0',
       url='https://github.com/zopefoundation/zope.sendmail',
       license='ZPL 2.1',
       description='Zope sendmail',