diff --git a/setup.py b/setup.py
index 7fa6225..070000f 100644
--- a/setup.py
+++ b/setup.py
@@ -38,7 +38,9 @@
     python_requires=">=3.7.0",
     install_requires=["aiohttp"],
     setup_requires=["pytest-runner"],
-    extras_require={"test": ["pytest", "pytest_httpserver", "pytest_asyncio"]},
+    extras_require={
+        "test": ["pytest", "pytest_httpserver", "pytest_asyncio", "flask"]
+    },
     classifiers=[
         "Programming Language :: Python :: 3",
         "License :: OSI Approved :: Apache Software License",