--- a/build/virtualenv_packages.txt
+++ b/build/virtualenv_packages.txt
@@ -44,16 +44,17 @@ mozilla.pth:testing/firefox-ui/harness
 mozilla.pth:testing/marionette/client
 mozilla.pth:testing/marionette/harness
 mozilla.pth:testing/marionette/harness/marionette_harness/runner/mixins/browsermob-proxy-py
 mozilla.pth:testing/marionette/puppeteer/firefox
 mozilla.pth:testing/talos
 packages.txt:testing/mozbase/packages.txt
 mozilla.pth:tools
 mozilla.pth:testing/web-platform
+mozilla.pth:testing/web-platform/tests/tools
 mozilla.pth:testing/web-platform/tests/tools/wptrunner
 mozilla.pth:testing/web-platform/tests/tools/wptserve
 mozilla.pth:testing/web-platform/tests/tools/six
 mozilla.pth:testing/xpcshell
 mozilla.pth:third_party/python/mock-1.0.0
 mozilla.pth:xpcom/typelib/xpt/tools
 mozilla.pth:tools/docs
 mozilla.pth:media/webrtc/trunk/tools/gyp/pylib