diff --git a/astroid/__pkginfo__.py b/astroid/__pkginfo__.py
index db402ae91..fd39f4558 100644
--- a/astroid/__pkginfo__.py
+++ b/astroid/__pkginfo__.py
@@ -2,5 +2,5 @@
 # For details: https://github.com/pylint-dev/astroid/blob/main/LICENSE
 # Copyright (c) https://github.com/pylint-dev/astroid/blob/main/CONTRIBUTORS.txt
 
-__version__ = "4.0.0-a1"
+__version__ = "4.0.0b1-dev0"
 version = __version__
diff --git a/tbump.toml b/tbump.toml
index 20b6e10db..6b84f2804 100644
--- a/tbump.toml
+++ b/tbump.toml
@@ -1,7 +1,7 @@
 github_url = "https://github.com/pylint-dev/astroid"
 
 [version]
-current = "4.0.0-a1"
+current = "4.0.0b1-dev0"
 regex = '''
 ^(?P<major>0|[1-9]\d*)
 \.