diff --git a/setup.cfg b/setup.cfg
index 5e200e19..a766dd94 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,6 +1,6 @@
 [metadata]
 name = Flask-SocketIO
-version = 5.2.0
+version = 5.2.1.dev0
 author = Miguel Grinberg
 author_email = miguel.grinberg@gmail.com
 description = Socket.IO integration for Flask applications