diff --git a/notebook/_version.py b/notebook/_version.py
index 4ddfb4b623..678319de40 100644
--- a/notebook/_version.py
+++ b/notebook/_version.py
@@ -5,7 +5,7 @@
 import re
 
 # Version string must appear intact for tbump versioning
-__version__ = '6.4.11'
+__version__ = '6.4.12.dev0'
 
 # Build up version_info tuple for backwards compatibility
 pattern = r'(?P<major>\d+).(?P<minor>\d+).(?P<patch>\d+)(?P<rest>.*)'