diff --git a/tox.ini b/tox.ini
index 4e5988c..1e708a7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,7 +9,13 @@ usedevelop = True
 setenv =
    VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
-passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
+passenv =
+  http_proxy
+  HTTP_PROXY
+  https_proxy
+  HTTPS_PROXY
+  no_proxy
+  NO_PROXY
 
 [testenv:venv]
 commands = {posargs}