diff --git a/src/flask/helpers.py b/src/flask/helpers.py
index 46244d29..5933f42a 100644
--- a/src/flask/helpers.py
+++ b/src/flask/helpers.py
@@ -7,6 +7,7 @@ from threading import RLock
 
 import werkzeug.utils
 from werkzeug.exceptions import NotFound
+from werkzeug.local import ContextVar
 from werkzeug.routing import BuildError
 from werkzeug.urls import url_quote
 
@@ -741,6 +742,11 @@ def run_async(func):
             "Install Flask with the 'async' extra in order to use async views."
         )
 
+    if ContextVar.__module__ == "werkzeug.local":
+        raise RuntimeError(
+            "async cannot be used with this combination of Python & Greenlet versions"
+        )
+
     @wraps(func)
     def outer(*args, **kwargs):
         """This function grabs the current context for the inner function.
diff --git a/tests/test_async.py b/tests/test_async.py
index d47d36ce..12784c34 100644
--- a/tests/test_async.py
+++ b/tests/test_async.py
@@ -1,10 +1,12 @@
 import asyncio
+import sys
 
 import pytest
 
 from flask import abort
 from flask import Flask
 from flask import request
+from flask.helpers import run_async
 
 
 @pytest.fixture(name="async_app")
@@ -23,6 +25,7 @@ def _async_app():
     return app
 
 
+@pytest.mark.skipif(sys.version_info < (3, 7), reason="requires Python >= 3.7")
 def test_async_request_context(async_app):
     test_client = async_app.test_client()
     response = test_client.get("/")
@@ -31,3 +34,9 @@ def test_async_request_context(async_app):
     assert b"POST" in response.get_data()
     response = test_client.get("/error")
     assert response.status_code == 412
+
+
+@pytest.mark.skipif(sys.version_info >= (3, 7), reason="should only raise Python < 3.7")
+def test_async_runtime_error():
+    with pytest.raises(RuntimeError):
+        run_async(None)
diff --git a/tox.ini b/tox.ini
index e0f666d8..cf12c0eb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -25,5 +25,8 @@ skip_install = true
 commands = pre-commit run --all-files --show-diff-on-failure
 
 [testenv:docs]
-deps = -r requirements/docs.txt
+deps =
+    -r requirements/docs.txt
+
+    https://github.com/pallets/werkzeug/archive/master.tar.gz
 commands = sphinx-build -W -b html -d {envtmpdir}/doctrees docs {envtmpdir}/html