diff --git a/python/CHANGELOG.rst b/python/CHANGELOG.rst
index 560023355c..94940e7c27 100644
--- a/python/CHANGELOG.rst
+++ b/python/CHANGELOG.rst
@@ -1,3 +1,7 @@
+--------------------
+[1.0.4] - 2026-XX-XX
+--------------------
+
 --------------------
 [1.0.3] - 2026-05-14
 --------------------
diff --git a/python/tskit/_version.py b/python/tskit/_version.py
index 1ca18ddc34..ba4310803d 100644
--- a/python/tskit/_version.py
+++ b/python/tskit/_version.py
@@ -1,4 +1,4 @@
 # Definitive location for the version number.
 # During development, should be x.y.z.devN
 # For beta should be x.y.zbN
-tskit_version = "1.0.3"
+tskit_version = "1.0.4.dev0"