diff --git a/tox.ini b/tox.ini
index 8c41988..055c13e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -80,6 +80,7 @@ deps =
     aiohttp: pytest-asyncio
     aiohttp: pytest-aiohttp
     httpx: httpx
+    httpx: pytest-asyncio
 depends =
   lint,{py35,py36,py37,py38,pypy3}-{requests,httplib2,urllib3,tornado4,boto3,httpx},{py35,py36,py37,py38}-{aiohttp}: cov-clean
   cov-report: lint,{py35,py36,py37,py38,pypy3}-{requests,httplib2,urllib3,tornado4,boto3},{py35,py36,py37,py38}-{aiohttp}