diff --git a/tox.ini b/tox.ini
index cdf6307..62e4415 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,6 +9,7 @@ install_command = pip install -U {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
+passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
 
 [testenv:venv]
 commands = {posargs}