diff --git a/CHANGES.rst b/CHANGES.rst
index 250385d68c..162d4c37ce 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -8,6 +8,12 @@ https://zope.readthedocs.io/en/2.13/CHANGES.html
 For the change log of the alpha versions see
 https://github.com/zopefoundation/Zope/blob/4.0a6/CHANGES.rst
 
+4.0.1 (unreleased)
+------------------
+
+- Nothing changed yet.
+
+
 4.0 (2019-05-10)
 ----------------
 
diff --git a/setup.py b/setup.py
index 3f59d185ac..fda1dbeb9a 100644
--- a/setup.py
+++ b/setup.py
@@ -29,7 +29,7 @@ def _read_file(filename):
 README = _read_file('README.rst')
 CHANGES = _read_file('CHANGES.rst')
 
-version = '4.0'
+version = '4.0.1.dev0'
 
 
 setup(