diff --git a/tox.ini b/tox.ini
index 11de86748b..a68acdbfeb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -71,7 +71,8 @@ commands =
 [testenv:{vendor,check-extern}]
 skip_install = True
 allowlist_externals = git, sh
-base_python = 3.8  # same as minimal version supported by setuptools
+base_python =
+	vendor: 3.8  # same as minimal version supported by setuptools
 deps =
 	path
 	cogapp