diff --git a/tox.ini b/tox.ini
index 8a06696ae..fbe3440a4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -2,6 +2,12 @@
 envlist = py36,py38,pep8
 minversion = 3.1.1
 skipsdist = True
+# Cap setuptools via virtualenv to prevent compatibility issue with victoria
+# branch's upper constraint of pbr package (5.5.0). Tox is also needed to be
+# constrained for the 'inner' tox to be installed with the constrained venv.
+requires =
+  virtualenv<20.24.0
+  tox<4
 
 [testenv]
 setenv = VIRTUAL_ENV={envdir}