diff --git a/pyproject.toml b/pyproject.toml
index 3b268f43..71fdcf2b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "poetry.core.masonry.api"
 
 [tool.poetry]
 name = "cleo"
-version = "2.1.0"
+version = "3.0.0.dev0"
 description = "Cleo allows you to create beautiful and testable command-line interfaces."
 authors = [
     "Sébastien Eustace <sebastien@eustace.io>"
diff --git a/src/cleo/__init__.py b/src/cleo/__init__.py
index 86e16da9..d30cca23 100644
--- a/src/cleo/__init__.py
+++ b/src/cleo/__init__.py
@@ -1,4 +1,4 @@
 from __future__ import annotations
 
 
-__version__ = "2.1.0"
+__version__ = "3.0.0.dev0"