diff --git a/nbclassic/_version.py b/nbclassic/_version.py
index d1c685793..7ffd79a44 100644
--- a/nbclassic/_version.py
+++ b/nbclassic/_version.py
@@ -5,7 +5,7 @@
 import re
 
 # Version string must appear intact for tbump versioning
-__version__ = '0.5.1'
+__version__ = '0.6.0.dev0'
 
 # Build up version_info tuple for backwards compatibility
 pattern = r'(?P<major>\d+).(?P<minor>\d+).(?P<patch>\d+)(?P<rest>.*)'
diff --git a/pyproject.toml b/pyproject.toml
index e3df1aee4..22129e2ae 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -28,7 +28,7 @@ post-version-spec = "dev"
 ignore-glob = ["docs/source/examples/Notebook/Working With Markdown Cells.ipynb", "docs-translations/**/README.md", "docs/source/contributing.rst", "docs/source/examples/Notebook/JavaScript Notebook Extensions.ipynb", "CHANGELOG.md", "nbclassic/static/components/**/*.*"]
 
 [tool.tbump.version]
-current = "0.5.1"
+current = "0.6.0.dev0"
 regex = '''
   (?P<major>\d+)\.(?P<minor>\d+)\.(?P<patch>\d+)
   ((?P<channel>a|b|rc|.dev)(?P<release>\d+))?