diff --git a/tox.ini b/tox.ini
index 4abef8d8..74426c3b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,4 +1,5 @@
 [tox]
+requires = virtualenv<20.22.0
 envlist = reset,py{27,27-portable,35,36,38,39,310},stats
 skip_missing_interpreters = true