diff --git a/poetry.lock b/poetry.lock
index 1c0a91b..644c2e4 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1938,5 +1938,5 @@ type = ["pytest-mypy"]
 
 [metadata]
 lock-version = "2.1"
-python-versions = ">=3.9"
-content-hash = "e665a081ee6654a22b546c4d7038099244942c1b26c9d1206fb2d8c70eb62e4b"
+python-versions = ">=3.9,<4.0"
+content-hash = "ee1ee3f36651623f20021a10e18992014a48a9a11f700611931cee9fa9e597a4"
diff --git a/pyproject.toml b/pyproject.toml
index d8b483b..9573b5b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -16,7 +16,7 @@ classifiers = [
     "Topic :: Software Development :: Libraries :: Python Modules",
     "Typing :: Typed",
 ]
-requires-python = ">=3.9"
+requires-python = ">=3.9,<4.0"
 dynamic = [ "version" ]
 dependencies = [
     "loguru",
diff --git a/{{cookiecutter.project_name}}/pyproject.toml b/{{cookiecutter.project_name}}/pyproject.toml
index 26d80ed..b33e33d 100644
--- a/{{cookiecutter.project_name}}/pyproject.toml
+++ b/{{cookiecutter.project_name}}/pyproject.toml
@@ -15,7 +15,7 @@ classifiers = [
     "Topic :: Software Development :: Libraries :: Python Modules",
     "Typing :: Typed",
 ]
-requires-python = ">=3.9"
+requires-python = ">=3.9,<4.0"
 dynamic = [ "version" ]
 dependencies = [
 ]