diff --git a/tests/upper-constraints.txt b/tests/upper-constraints.txt
index 75f337856..2a335e533 100644
--- a/tests/upper-constraints.txt
+++ b/tests/upper-constraints.txt
@@ -2,7 +2,7 @@
 # pip dependency resolver from spending too much time backtracking.
 attrs>=20.2.0
 Automat>=0.8.0
-botocore>=1.20.3
+botocore>=1.20.30
 itemadapter>=0.1.1
 itemloaders>=1.0.3
 lxml>=4.6.1
diff --git a/tox.ini b/tox.ini
index 86ae951b5..e0c69350e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -13,7 +13,8 @@ deps =
     # mitmproxy does not support PyPy
     # mitmproxy does not support Windows when running Python < 3.7
     # Python 3.9+ requires https://github.com/mitmproxy/mitmproxy/commit/8e5e43de24c9bc93092b63efc67fbec029a9e7fe
-    mitmproxy >= 5.3.0; python_version >= '3.9' and implementation_name != 'pypy'
+    # mitmproxy >= 5.3.0 requires h2 >= 4.0, Twisted 21.2 requires h2 < 4.0
+    #mitmproxy >= 5.3.0; python_version >= '3.9' and implementation_name != 'pypy'
     mitmproxy >= 4.0.4; python_version >= '3.7' and python_version < '3.9' and implementation_name != 'pypy'
     mitmproxy >= 4.0.4, < 5; python_version >= '3.6' and python_version < '3.7' and platform_system != 'Windows' and implementation_name != 'pypy'
     # Extras