diff --git a/poetry.lock b/poetry.lock
index c217b98..c93be9e 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -61,10 +61,10 @@ optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
 
 [package.extras]
-dev = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "six", "mypy", "pytest-mypy-plugins", "zope.interface", "furo", "sphinx", "sphinx-notfound-page", "pre-commit"]
-docs = ["furo", "sphinx", "zope.interface", "sphinx-notfound-page"]
-tests = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "six", "mypy", "pytest-mypy-plugins", "zope.interface"]
-tests_no_zope = ["coverage[toml] (>=5.0.2)", "hypothesis", "pympler", "pytest (>=4.3.0)", "six", "mypy", "pytest-mypy-plugins"]
+dev = ["coverage[toml] (>=5.0.2)", "furo", "hypothesis", "mypy", "pre-commit", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "six", "sphinx", "sphinx-notfound-page", "zope.interface"]
+docs = ["furo", "sphinx", "sphinx-notfound-page", "zope.interface"]
+tests = ["coverage[toml] (>=5.0.2)", "hypothesis", "mypy", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "six", "zope.interface"]
+tests_no_zope = ["coverage[toml] (>=5.0.2)", "hypothesis", "mypy", "pympler", "pytest (>=4.3.0)", "pytest-mypy-plugins", "six"]
 
 [[package]]
 name = "black"
@@ -208,8 +208,8 @@ typing-extensions = {version = ">=3.6.4", markers = "python_version < \"3.8\""}
 zipp = ">=0.5"
 
 [package.extras]
-docs = ["sphinx", "jaraco.packaging (>=8.2)", "rst.linker (>=1.9)"]
-testing = ["pytest (>=4.6)", "pytest-checkdocs (>=2.4)", "pytest-flake8", "pytest-cov", "pytest-enabler (>=1.0.1)", "packaging", "pep517", "pyfakefs", "flufl.flake8", "pytest-black (>=0.3.7)", "pytest-mypy", "importlib-resources (>=1.3)"]
+docs = ["jaraco.packaging (>=8.2)", "rst.linker (>=1.9)", "sphinx"]
+testing = ["flufl.flake8", "importlib-resources (>=1.3)", "packaging", "pep517", "pyfakefs", "pytest (>=4.6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=2.4)", "pytest-cov", "pytest-enabler (>=1.0.1)", "pytest-flake8", "pytest-mypy"]
 
 [[package]]
 name = "iniconfig"
@@ -379,18 +379,18 @@ testing = ["coverage", "hypothesis (>=5.7.1)"]
 
 [[package]]
 name = "pytest-cov"
-version = "2.11.1"
+version = "4.0.0"
 description = "Pytest plugin for measuring coverage."
 category = "dev"
 optional = false
-python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*"
+python-versions = ">=3.6"
 
 [package.dependencies]
-coverage = ">=5.2.1"
+coverage = {version = ">=5.2.1", extras = ["toml"]}
 pytest = ">=4.6"
 
 [package.extras]
-testing = ["fields", "hunter", "process-tests (==2.0.2)", "six", "pytest-xdist", "virtualenv"]
+testing = ["fields", "hunter", "process-tests", "pytest-xdist", "six", "virtualenv"]
 
 [[package]]
 name = "pyyaml"
@@ -445,7 +445,7 @@ virtualenv = ">=16.0.0,<20.0.0 || >20.0.0,<20.0.1 || >20.0.1,<20.0.2 || >20.0.2,
 
 [package.extras]
 docs = ["pygments-github-lexers (>=0.0.5)", "sphinx (>=2.0.0)", "sphinxcontrib-autoprogram (>=0.1.5)", "towncrier (>=18.5.0)"]
-testing = ["flaky (>=3.4.0)", "freezegun (>=0.3.11)", "psutil (>=5.6.1)", "pytest (>=4.0.0)", "pytest-cov (>=2.5.1)", "pytest-mock (>=1.10.0)", "pytest-randomly (>=1.0.0)", "pytest-xdist (>=1.22.2)", "pathlib2 (>=2.3.3)"]
+testing = ["flaky (>=3.4.0)", "freezegun (>=0.3.11)", "pathlib2 (>=2.3.3)", "psutil (>=5.6.1)", "pytest (>=4.0.0)", "pytest-cov (>=2.5.1)", "pytest-mock (>=1.10.0)", "pytest-randomly (>=1.0.0)", "pytest-xdist (>=1.22.2)"]
 
 [[package]]
 name = "typed-ast"
@@ -480,7 +480,7 @@ six = ">=1.9.0,<2"
 
 [package.extras]
 docs = ["proselint (>=0.10.2)", "sphinx (>=3)", "sphinx-argparse (>=0.2.5)", "sphinx-rtd-theme (>=0.4.3)", "towncrier (>=19.9.0rc1)"]
-testing = ["coverage (>=4)", "coverage-enable-subprocess (>=1)", "flaky (>=3)", "pytest (>=4)", "pytest-env (>=0.6.2)", "pytest-freezegun (>=0.4.1)", "pytest-mock (>=2)", "pytest-randomly (>=1)", "pytest-timeout (>=1)", "packaging (>=20.0)", "xonsh (>=0.9.16)"]
+testing = ["coverage (>=4)", "coverage-enable-subprocess (>=1)", "flaky (>=3)", "packaging (>=20.0)", "pytest (>=4)", "pytest-env (>=0.6.2)", "pytest-freezegun (>=0.4.1)", "pytest-mock (>=2)", "pytest-randomly (>=1)", "pytest-timeout (>=1)", "xonsh (>=0.9.16)"]
 
 [[package]]
 name = "yarl"
@@ -504,13 +504,13 @@ optional = false
 python-versions = ">=3.6"
 
 [package.extras]
-docs = ["sphinx", "jaraco.packaging (>=8.2)", "rst.linker (>=1.9)"]
-testing = ["pytest (>=4.6)", "pytest-checkdocs (>=1.2.3)", "pytest-flake8", "pytest-cov", "pytest-enabler", "jaraco.itertools", "func-timeout", "pytest-black (>=0.3.7)", "pytest-mypy"]
+docs = ["jaraco.packaging (>=8.2)", "rst.linker (>=1.9)", "sphinx"]
+testing = ["func-timeout", "jaraco.itertools", "pytest (>=4.6)", "pytest-black (>=0.3.7)", "pytest-checkdocs (>=1.2.3)", "pytest-cov", "pytest-enabler", "pytest-flake8", "pytest-mypy"]
 
 [metadata]
 lock-version = "1.1"
 python-versions = "^3.7"
-content-hash = "26fee507bafce2854af5ef0d5a4173482409dfb82be4c19ac8c190e31a0e5d9d"
+content-hash = "5997ba3d37c8986cc870c091cf41e0f6efb1f392ee786dc4b50443ed9b1be6e6"
 
 [metadata.files]
 aiohttp = [
@@ -773,8 +773,8 @@ pytest-asyncio = [
     {file = "pytest_asyncio-0.15.1-py3-none-any.whl", hash = "sha256:3042bcdf1c5d978f6b74d96a151c4cfb9dcece65006198389ccd7e6c60eb1eea"},
 ]
 pytest-cov = [
-    {file = "pytest-cov-2.11.1.tar.gz", hash = "sha256:359952d9d39b9f822d9d29324483e7ba04a3a17dd7d05aa6beb7ea01e359e5f7"},
-    {file = "pytest_cov-2.11.1-py2.py3-none-any.whl", hash = "sha256:bdb9fdb0b85a7cc825269a4c56b48ccaa5c7e365054b6038772c32ddcdc969da"},
+    {file = "pytest-cov-4.0.0.tar.gz", hash = "sha256:996b79efde6433cdbd0088872dbc5fb3ed7fe1578b68cdbba634f14bb8dd0470"},
+    {file = "pytest_cov-4.0.0-py3-none-any.whl", hash = "sha256:2feb1b751d66a8bd934e5edfa2e961d11309dc37b73b0eabe73b5945fee20f6b"},
 ]
 pyyaml = [
     {file = "PyYAML-5.4.1-cp27-cp27m-macosx_10_9_x86_64.whl", hash = "sha256:3b2b1824fe7112845700f815ff6a489360226a5609b96ec2190a45e62a9fc922"},
diff --git a/pyproject.toml b/pyproject.toml
index 503cd2d..09694a9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -30,7 +30,7 @@ tox = "^3.20"
 pytest = "^6.0"
 aioresponses = "^0.7"
 pytest-asyncio = "^0.15"
-pytest-cov = "^2.10"
+pytest-cov = "^4.0"
 
 [tool.tox]
 legacy_tox_ini = """