diff --git a/playbooks/legacy/grenade-devstack-watcher/run.yaml b/playbooks/legacy/grenade-devstack-watcher/run.yaml
index 62eddf2bd..76717ac18 100644
--- a/playbooks/legacy/grenade-devstack-watcher/run.yaml
+++ b/playbooks/legacy/grenade-devstack-watcher/run.yaml
@@ -40,7 +40,7 @@
 
           export DEVSTACK_GATE_TEMPEST_NOTESTS=1
           export DEVSTACK_GATE_GRENADE=pullup
-
+          export DEVSTACK_GATE_USE_PYTHON3=True
           export BRANCH_OVERRIDE=default
           if [ "$BRANCH_OVERRIDE" != "default" ] ; then
               export OVERRIDE_ZUUL_BRANCH=$BRANCH_OVERRIDE