diff --git a/gen-requirements.txt b/gen-requirements.txt
index 2512362a9..203cd7b7b 100644
--- a/gen-requirements.txt
+++ b/gen-requirements.txt
@@ -7,3 +7,5 @@ requests
 tomli
 tomli_w
 hatch
+# TODO: stick with virtualenv < 21 until a new hatch release
+virtualenv<21