diff --git a/setup.cfg b/setup.cfg
index 9512c39..a24759f 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -57,7 +57,7 @@ ignore =
     E203  # Whitespace before ':', preferred formatting for black.
 
 [bumpver]
-current_version = "v0.4.0"
+current_version = "v0.5.0b0"
 version_pattern = "vMAJOR.MINOR.PATCH[PYTAGNUM]"
 commit_message = "Bump version {old_version} -> {new_version}"
 commit = True
diff --git a/widget_bandsplot/version.py b/widget_bandsplot/version.py
index 6a9beea..331dfae 100644
--- a/widget_bandsplot/version.py
+++ b/widget_bandsplot/version.py
@@ -1 +1 @@
-__version__ = "0.4.0"
+__version__ = "0.5.0b0"