1 files changed, 1 insertions, 0 deletions

diff --git a/tox.ini b/tox.ini
index 64a1929..86bf386 100644
--- a/tox.ini
+++ b/tox.ini
@@ -2,6 +2,7 @@
 minversion = 3.2.0
 envlist = py3,pep8
 ignore_basepython_conflict = true
+requires = virtualenv<20.8
 
 [testenv]
 basepython = python3