diff --git a/tests/tests.yml b/tests/tests.yml
index 4fcdd28..c6263a7 100644
--- a/tests/tests.yml
+++ b/tests/tests.yml
@@ -10,7 +10,7 @@
     tests:
     - smoke:
         dir: python/smoke
-        run: VERSION=3.6 ./venv.sh
+        run: VERSION=3.6 TOX_REQUIRES="virtualenv<20.22.0" ./venv.sh
     - marshalparser:
         dir: python/marshalparser
         run: VERSION=3.6 SAMPLE=10 test_marshalparser_compatibility.sh