diff --git a/CHANGES.rst b/CHANGES.rst
index 4a0fe31..cdee135 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -2,6 +2,12 @@
  Changes
 =========
 
+5.2.0 (unreleased)
+==================
+
+- Nothing changed yet.
+
+
 5.1.0 (2020-02-14)
 ==================
 
diff --git a/setup.py b/setup.py
index a2b5441..0830708 100644
--- a/setup.py
+++ b/setup.py
@@ -127,7 +127,7 @@ def __str__(self):
 
 
 setup(name='zope.security',
-      version='5.1.0',
+      version='5.2.0.dev0',
       author='Zope Foundation and Contributors',
       author_email='zope-dev@zope.org',
       description='Zope Security Framework',