Bump version to 3.5.3.dev
diff --git a/setup.py b/setup.py
index 2ce84f2..557aeea 100644
--- a/setup.py
+++ b/setup.py
@@ -9,7 +9,7 @@
                      'to install the typing package.\n')
     exit(1)
 
-version = '3.5.2.2'
+version = '3.5.3.dev'
 description = 'Type Hints for Python'
 long_description = '''\
 Typing -- Type Hints for Python