diff --git a/tox.ini b/tox.ini
index e45c1c125..febf1a2d0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -12,6 +12,8 @@ envlist = py27,cover,lint
 # loops, especially on Travis
 
 [testenv]
+# packages installed separately to ensure that dowstream deps problems
+# are detected, c.f. #1002
 commands =
     pip install -e acme[testing]
     nosetests -v acme