diff --git a/CHANGELOG.md b/CHANGELOG.md
index 62bf9a58d..a3599f28b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,8 @@ https://keepachangelog.com/en/1.0.0/
 https://semver.org/spec/v2.0.0.html
 
 
+## [Unreleased]
+
 ## [2.0.0] - 2025-06-13
 
 ### Added
diff --git a/src/_geoslib.pyx b/src/_geoslib.pyx
index bc050cc45..2aab76867 100644
--- a/src/_geoslib.pyx
+++ b/src/_geoslib.pyx
@@ -2,7 +2,7 @@ import sys
 import numpy
 cimport numpy as cnp
 
-__version__ = "2.0.0"
+__version__ = "2.1.0.dev0"
 
 
 # Need some Python C-API functions for strings.
diff --git a/src/mpl_toolkits/basemap/__init__.py b/src/mpl_toolkits/basemap/__init__.py
index 45a925434..46458b95b 100644
--- a/src/mpl_toolkits/basemap/__init__.py
+++ b/src/mpl_toolkits/basemap/__init__.py
@@ -48,7 +48,7 @@
 from . proj import Proj
 
 
-__version__ = "2.0.0"
+__version__ = "2.1.0.dev0"
 
 # basemap data files now installed in lib/matplotlib/toolkits/basemap/data
 # check to see if environment variable BASEMAPDATA set to a directory,