diff --git a/Makefile b/Makefile
index ddda90e6f..42f5ea801 100644
--- a/Makefile
+++ b/Makefile
@@ -14,6 +14,9 @@ $(VENV_NAME)/bin/activate: setup.py
 test: venv
 	@${VENV_NAME}/bin/tox -p auto $(TOX_ARGS)
 
+test-nomock: venv
+	@${VENV_NAME}/bin/tox -p auto -- --nomock $(TOX_ARGS)
+
 ci: venv
 	@${VENV_NAME}/bin/python setup.py test -a "-n auto --cov=stripe"
 
diff --git a/setup.py b/setup.py
index 18fdda8b7..522e56906 100644
--- a/setup.py
+++ b/setup.py
@@ -55,7 +55,8 @@ def run_tests(self):
     ],
     python_requires=">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*",
     tests_require=[
-        "pytest >= 4.6.2, < 4.7",
+        'pytest >= 4.6.2, < 4.7; python_version < "3.5"',
+        'pytest >= 6.0.0; python_version >= "3.5"',
         "pytest-mock >= 2.0.0",
         "pytest-xdist >= 1.31.0",
         "pytest-cov >= 2.8.1",
diff --git a/tests/api_resources/test_source.py b/tests/api_resources/test_source.py
index dc6bd9f75..fa36a158e 100644
--- a/tests/api_resources/test_source.py
+++ b/tests/api_resources/test_source.py
@@ -53,7 +53,7 @@ def test_is_detachable_when_attached(self, request_mock):
             "delete", "/v1/customers/cus_123/sources/%s" % TEST_RESOURCE_ID
         )
 
-    def test_is_not_detachable_when_unattached(self):
+    def test_is_not_detachable_when_unattached(self, request_mock):
         resource = stripe.Source.retrieve(TEST_RESOURCE_ID)
         with pytest.raises(stripe.error.InvalidRequestError):
             resource.detach()
diff --git a/tests/conftest.py b/tests/conftest.py
index da371ad24..a91925f49 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -31,27 +31,47 @@ def stop_stripe_mock():
     StripeMock.stop()
 
 
-try:
-    resp = urlopen("http://localhost:%s/" % MOCK_PORT)
-    info = resp.info()
-except HTTPError as e:
-    info = e.info()
-except Exception:
-    sys.exit(
-        "Couldn't reach stripe-mock at `localhost:%s`. Is "
-        "it running? Please see README for setup instructions." % MOCK_PORT
+def pytest_configure(config):
+    if not config.getoption("--nomock"):
+        try:
+            resp = urlopen("http://localhost:%s/" % MOCK_PORT)
+            info = resp.info()
+            version = info.get("Stripe-Mock-Version")
+            if version != "master" and StrictVersion(version) < StrictVersion(
+                MOCK_MINIMUM_VERSION
+            ):
+                sys.exit(
+                    "Your version of stripe-mock (%s) is too old. The minimum "
+                    "version to run this test suite is %s. Please "
+                    "see its repository for upgrade instructions."
+                    % (version, MOCK_MINIMUM_VERSION)
+                )
+
+        except HTTPError as e:
+            info = e.info()
+        except Exception:
+            sys.exit(
+                "Couldn't reach stripe-mock at `localhost:%s`. Is "
+                "it running? Please see README for setup instructions."
+                % MOCK_PORT
+            )
+
+
+def pytest_addoption(parser):
+    parser.addoption(
+        "--nomock",
+        action="store_true",
+        help="only run tests that don't need stripe-mock",
     )
 
-version = info.get("Stripe-Mock-Version")
-if version != "master" and StrictVersion(version) < StrictVersion(
-    MOCK_MINIMUM_VERSION
-):
-    sys.exit(
-        "Your version of stripe-mock (%s) is too old. The minimum "
-        "version to run this test suite is %s. Please "
-        "see its repository for upgrade instructions."
-        % (version, MOCK_MINIMUM_VERSION)
-    )
+
+def pytest_runtest_setup(item):
+    if "request_mock" in item.fixturenames and item.config.getoption(
+        "--nomock"
+    ):
+        pytest.skip(
+            "run stripe-mock locally and remove --nomock flag to run skipped tests"
+        )
 
 
 @pytest.fixture(autouse=True)
diff --git a/tox.ini b/tox.ini
index 1abb46510..2bb6e5b0c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -36,5 +36,5 @@ skip_install = true
 description = run static analysis and style check using flake8
 basepython = python2.7
 deps = flake8
-commands = python -m flake8 --show-source stripe tests setup.py {posargs}
+commands = python -m flake8 --show-source stripe tests setup.py
 skip_install = true