diff --git a/tobiko/openstack/stacks/_cirros.py b/tobiko/openstack/stacks/_cirros.py
index 4850391a0..c3f312238 100644
--- a/tobiko/openstack/stacks/_cirros.py
+++ b/tobiko/openstack/stacks/_cirros.py
@@ -14,8 +14,10 @@
 from __future__ import absolute_import
 
 import io
+import os
 import typing
 
+from oslo_concurrency import lockutils
 from paramiko import sftp_file
 
 from tobiko import config
@@ -30,6 +32,7 @@ import tobiko.tripleo
 from tobiko.openstack.stacks import _hot
 
 CONF = config.CONF
+LOCK_DIR = os.path.expanduser(CONF.tobiko.common.lock_dir)
 
 CIRROS_IMAGE_VERSION = '0.5.2'
 
@@ -54,6 +57,11 @@ class CirrosImageFixture(glance.URLGlanceImageFixture):
         # when using recent Paramiko versions (>= 2.9.2)
         'pubkeys': ['rsa-sha2-256', 'rsa-sha2-512']}
 
+    @lockutils.synchronized(
+        'cirros_image_setup_fixture', external=True, lock_path=LOCK_DIR)
+    def setup_fixture(self):
+        super(CirrosImageFixture, self).setup_fixture()
+
 
 class CirrosFlavorStackFixture(_nova.FlavorStackFixture):
     ram = 128
diff --git a/tobiko/openstack/stacks/_ubuntu.py b/tobiko/openstack/stacks/_ubuntu.py
index 2c3c86301..b741ebc1a 100644
--- a/tobiko/openstack/stacks/_ubuntu.py
+++ b/tobiko/openstack/stacks/_ubuntu.py
@@ -13,8 +13,11 @@
 #    under the License.
 from __future__ import absolute_import
 
+import os
 import typing
 
+from oslo_concurrency import lockutils
+
 import tobiko
 from tobiko import config
 from tobiko.openstack import glance
@@ -25,6 +28,7 @@ from tobiko.shell import sh
 
 
 CONF = config.CONF
+LOCK_DIR = os.path.expanduser(CONF.tobiko.common.lock_dir)
 
 
 class UbuntuMinimalImageFixture(glance.FileGlanceImageFixture):
@@ -38,6 +42,11 @@ class UbuntuMinimalImageFixture(glance.FileGlanceImageFixture):
     disabled_algorithms = CONF.tobiko.ubuntu.disabled_algorithms
     is_reachable_timeout = CONF.tobiko.nova.ubuntu_is_reachable_timeout
 
+    @lockutils.synchronized(
+        'ubuntu_minimal_setup_fixture', external=True, lock_path=LOCK_DIR)
+    def setup_fixture(self):
+        super(UbuntuMinimalImageFixture, self).setup_fixture()
+
 
 IPERF3_SERVICE_FILE = """
 [Unit]