diff --git a/tox.ini b/tox.ini
index 329d2d7488..bbbe2659ea 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,6 +9,8 @@ deps =
     # Possible workaround for errors in Travis CI under some Pythons
     pip>=19.1
     wheel
+    # FIXME: Drop this temporary unreleased dependency before merging the PR:
+    h11 @ git+https://github.com/duper51/h11@master
 commands =
     pytest --testmon-off {posargs}
     codecov -f coverage.xml -X gcov