diff --git a/tox.ini b/tox.ini
index 98e185cfa..a1ed23cf7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -59,7 +59,7 @@ basepython = python2.7
 # duplicate code checking; if one of the commands fails, others will
 # continue, but tox return code will reflect previous error
 commands =
-    pip install -e acme -e .[dns,dev] -e letsencrypt-apache -e letsencrypt-nginx -e letsencrypt-compatibility-test -e letshelp-letsencrypt
+    pip install -e acme[dns] -e .[dns,dev] -e letsencrypt-apache -e letsencrypt-nginx -e letsencrypt-compatibility-test -e letshelp-letsencrypt
     ./pep8.travis.sh
     pylint --rcfile=.pylintrc letsencrypt
     pylint --rcfile=.pylintrc acme/acme