diff --git a/__pkginfo__.py b/__pkginfo__.py
index 257f0a0..9b7a506 100644
--- a/__pkginfo__.py
+++ b/__pkginfo__.py
@@ -3,6 +3,6 @@
 __all__ = ["extras_require"]
 
 extras_require = {
-		"sphinx": ["sphinx>=3.4.0", "sphinx-jinja2-compat>=0.1.1", "sphinx-toolbox>=2.16.0"],
-		"all": ["sphinx>=3.4.0", "sphinx-jinja2-compat>=0.1.1", "sphinx-toolbox>=2.16.0"]
+		"sphinx": ["sphinx>=3.4.0,<9", "sphinx-jinja2-compat>=0.1.1", "sphinx-toolbox>=2.16.0"],
+		"all": ["sphinx>=3.4.0,<9", "sphinx-jinja2-compat>=0.1.1", "sphinx-toolbox>=2.16.0"]
 		}
diff --git a/enum_tools/__init__.py b/enum_tools/__init__.py
index d0cabbf..b966a84 100644
--- a/enum_tools/__init__.py
+++ b/enum_tools/__init__.py
@@ -33,7 +33,7 @@
 __author__: str = "Dominic Davis-Foster"
 __copyright__: str = "2020 Dominic Davis-Foster"
 __license__: str = "GNU Lesser General Public License v3 or later (LGPLv3+)"
-__version__: str = "0.13.0"
+__version__: str = "0.13.1"
 __email__: str = "dominic@davis-foster.co.uk"
 
 __all__ = [
diff --git a/pyproject.toml b/pyproject.toml
index 62f635e..88c78ad 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "whey"
 
 [project]
 name = "enum-tools"
-version = "0.13.0"
+version = "0.13.1"
 description = "Tools to expand Python's enum module."
 readme = "README.rst"
 keywords = [ "documentation", "enum", "sphinx", "sphinx-extension",]
@@ -24,8 +24,8 @@ Homepage = "https://github.com/domdfcoding/enum_tools"
 Documentation = "https://enum-tools.readthedocs.io/en/latest"
 
 [project.optional-dependencies]
-sphinx = [ "sphinx>=3.4.0", "sphinx-jinja2-compat>=0.1.1", "sphinx-toolbox>=2.16.0",]
-all = [ "sphinx>=3.4.0", "sphinx-jinja2-compat>=0.1.1", "sphinx-toolbox>=2.16.0",]
+sphinx = [ "sphinx<9,>=3.4.0", "sphinx-jinja2-compat>=0.1.1", "sphinx-toolbox>=2.16.0",]
+all = [ "sphinx<9,>=3.4.0", "sphinx-jinja2-compat>=0.1.1", "sphinx-toolbox>=2.16.0",]
 
 [tool.whey]
 base-classifiers = [
diff --git a/repo_helper.yml b/repo_helper.yml
index 42c2adf..ed27c94 100644
--- a/repo_helper.yml
+++ b/repo_helper.yml
@@ -4,7 +4,7 @@ modname: enum_tools
 copyright_years: "2020-2022"
 author: "Dominic Davis-Foster"
 email: "dominic@davis-foster.co.uk"
-version: "0.13.0"
+version: "0.13.1"
 username: "domdfcoding"
 license: 'LGPLv3+'
 short_desc: "Tools to expand Python's enum module."
@@ -151,7 +151,7 @@ keywords:
 
 extras_require:
   sphinx:
-   - sphinx>=3.4.0
+   - sphinx>=3.4.0,<9
    - sphinx-toolbox>=2.16.0
    - sphinx-jinja2-compat>=0.1.1