diff --git a/playbooks/legacy/blazar-devstack-dsvm-py35/run.yaml b/playbooks/legacy/blazar-devstack-dsvm-py35/run.yaml
index 9f529b2f..6d0b78dd 100644
--- a/playbooks/legacy/blazar-devstack-dsvm-py35/run.yaml
+++ b/playbooks/legacy/blazar-devstack-dsvm-py35/run.yaml
@@ -57,6 +57,7 @@
           export PROJECTS="openstack/python-blazarclient $PROJECTS"
           export PROJECTS="openstack/blazar-tempest-plugin $PROJECTS"
           export DEVSTACK_GATE_TEMPEST_REGEX="blazar_tempest_plugin"
+          export TEMPEST_CONCURRENCY=1
           cp devstack-gate/devstack-vm-gate-wrap.sh ./safe-devstack-vm-gate-wrap.sh
           ./safe-devstack-vm-gate-wrap.sh
         executable: /bin/bash
diff --git a/playbooks/legacy/blazar-devstack-dsvm/run.yaml b/playbooks/legacy/blazar-devstack-dsvm/run.yaml
index 1e9c0271..8a0c3a09 100644
--- a/playbooks/legacy/blazar-devstack-dsvm/run.yaml
+++ b/playbooks/legacy/blazar-devstack-dsvm/run.yaml
@@ -49,6 +49,7 @@
           export PROJECTS="openstack/python-blazarclient $PROJECTS"
           export PROJECTS="openstack/blazar-tempest-plugin $PROJECTS"
           export DEVSTACK_GATE_TEMPEST_REGEX="blazar_tempest_plugin"
+          export TEMPEST_CONCURRENCY=1
           cp devstack-gate/devstack-vm-gate-wrap.sh ./safe-devstack-vm-gate-wrap.sh
           ./safe-devstack-vm-gate-wrap.sh
         executable: /bin/bash