diff --git a/tox.ini b/tox.ini
index 323a9cd0..85167558 100644
--- a/tox.ini
+++ b/tox.ini
@@ -23,6 +23,11 @@ deps =
     -r{toxinidir}/test-requirements.txt
 commands = pytest --cov=./zaza/ {posargs} {toxinidir}/unit_tests
 
+[testenv:.pkg]
+pass_env =
+  # NOTE: This is required because tox>=4 will not pass env. See https://github.com/tox-dev/tox/issues/2543.
+  TEST_JUJU3
+
 [testenv:py3]
 basepython = python3