diff --git a/CHANGES.rst b/CHANGES.rst
index 712c1e8..ff10868 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,6 +1,12 @@
 Change log
 ==========
 
+5.1 (unreleased)
+----------------
+
+- Nothing changed yet.
+
+
 5.0 (2025-01-15)
 ----------------
 
diff --git a/setup.py b/setup.py
index 2f5fd3f..1ce6feb 100644
--- a/setup.py
+++ b/setup.py
@@ -20,7 +20,7 @@
 
 setup(
     name='roman',
-    version='5.0',
+    version='5.1.dev0',
     author="Mark Pilgrim",
     maintainer="Zope Foundation and Contributors",
     maintainer_email="zope-dev@zope.dev",