diff --git a/playbooks/tox/run-both.yaml b/playbooks/tox/run-both.yaml
index e4043d8231..0f8af920e4 100644
--- a/playbooks/tox/run-both.yaml
+++ b/playbooks/tox/run-both.yaml
@@ -6,6 +6,12 @@
       bindep_profile: test
       bindep_dir: "{{ zuul_work_dir }}"
     - test-setup
-    - ensure-tox
+    # NOTE(gmann): Pinning tox<4.0.0 for stable/zed and lower. Tox 4.0.0
+    # released after zed was released and has some incompatible changes
+    # and it is ok not to fix the issues caused by tox 4.0.0 in stable
+    # beanches jobs. We can continue testing the stable/zed and lower
+    # branches with tox<4.0.0
+    - role: ensure-tox
+      ensure_tox_version: "<4"
     - get-devstack-os-environment
     - tox