diff --git a/requirements/dev.in b/requirements/dev.in
index 44c2c39f3..c9bf8bcad 100644
--- a/requirements/dev.in
+++ b/requirements/dev.in
@@ -8,7 +8,7 @@
 -r pip.pip
 
 # PyPI requirements for running tests.
-tox
+-r tox.pip
 -r pytest.pip
 
 # for linting.