diff --git a/poetry.lock b/poetry.lock
index 39395ef..f633936 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -428,7 +428,7 @@ name = "pyyaml"
 version = "5.3.1"
 description = "YAML parser and emitter for Python"
 category = "dev"
-optional = false
+optional = true
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
 
 [[package]]
@@ -504,17 +504,17 @@ python-versions = "*"
 
 [[package]]
 name = "sphinx"
-version = "3.1.2"
+version = "4.0.3"
 description = "Python documentation generator"
 category = "dev"
 optional = true
-python-versions = ">=3.5"
+python-versions = ">=3.6"
 
 [package.dependencies]
 alabaster = ">=0.7,<0.8"
 babel = ">=1.3"
 colorama = {version = ">=0.3.5", markers = "sys_platform == \"win32\""}
-docutils = ">=0.12"
+docutils = ">=0.14,<0.18"
 imagesize = "*"
 Jinja2 = ">=2.3"
 packaging = "*"
@@ -530,8 +530,8 @@ sphinxcontrib-serializinghtml = "*"
 
 [package.extras]
 docs = ["sphinxcontrib-websupport"]
-lint = ["flake8 (>=3.5.0)", "flake8-import-order", "mypy (>=0.780)", "docutils-stubs"]
-test = ["pytest", "pytest-cov", "html5lib", "typed-ast", "cython"]
+lint = ["flake8 (>=3.5.0)", "isort", "mypy (>=0.900)", "docutils-stubs", "types-typed-ast", "types-pkg-resources", "types-requests"]
+test = ["pytest", "pytest-cov", "html5lib", "cython", "typed-ast"]
 
 [[package]]
 name = "sphinx-rtd-theme"
@@ -703,7 +703,7 @@ travis-ci = []
 [metadata]
 lock-version = "1.1"
 python-versions = "^3.6"
-content-hash = "a18078e1b4a0363f1c0171e88d27f24b80e5a9e8d460836525b282702be6458f"
+content-hash = "f56a79d11c55de3e734f5c1d48be39c8b63d11739c1ec19d413a9b72a2f2b553"
 
 [metadata.files]
 alabaster = [
@@ -986,8 +986,8 @@ snowballstemmer = [
     {file = "snowballstemmer-1.2.1.tar.gz", hash = "sha256:919f26a68b2c17a7634da993d91339e288964f93c274f1343e3bbbe2096e1128"},
 ]
 sphinx = [
-    {file = "Sphinx-3.1.2-py3-none-any.whl", hash = "sha256:97dbf2e31fc5684bb805104b8ad34434ed70e6c588f6896991b2fdfd2bef8c00"},
-    {file = "Sphinx-3.1.2.tar.gz", hash = "sha256:b9daeb9b39aa1ffefc2809b43604109825300300b987a24f45976c001ba1a8fd"},
+    {file = "Sphinx-4.0.3-py3-none-any.whl", hash = "sha256:5747f3c855028076fcff1e4df5e75e07c836f0ac11f7df886747231092cfe4ad"},
+    {file = "Sphinx-4.0.3.tar.gz", hash = "sha256:dff357e6a208eb7edb2002714733ac21a9fe597e73609ff417ab8cf0c6b4fbb8"},
 ]
 sphinx-rtd-theme = [
     {file = "sphinx_rtd_theme-0.5.0-py2.py3-none-any.whl", hash = "sha256:373413d0f82425aaa28fb288009bf0d0964711d347763af2f1b65cafcb028c82"},
diff --git a/pyproject.toml b/pyproject.toml
index 7a5815f..1b274cb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -40,7 +40,7 @@ responses = "^0.10.15"
 pytest-runner = "^5.3"
 towncrier = {version = "^19.2", optional = true}
 tox = "^3.19"
-sphinx = {version = "^3.1", optional = true}
+sphinx = {version = "^4.0", optional = true}
 sphinx_rtd_theme = {version = "^0.5.0", optional = true}
 pre-commit = {version = "^2.1", optional = true}