diff --git a/Containerfile.tests.el7 b/Containerfile.tests.el7
index 06a9b789..406fbb80 100644
--- a/Containerfile.tests.el7
+++ b/Containerfile.tests.el7
@@ -4,7 +4,7 @@
 FROM quay.io/centos/centos:7
 RUN set -exo pipefail \
     && yum install -y https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm \
-    && yum install -y python-requests m2crypto libvirt-python python-lxml python-libguestfs pytest python-monotonic libvirt \
+    && yum install -y python-requests m2crypto libvirt-python python-lxml python-libguestfs pytest python-monotonic python-mock libvirt \
     && yum clean all \
     && rm -rf /var/cache/* /var/log/yum*
 
diff --git a/README b/README
index 5f2c983c..c53e23d9 100644
--- a/README
+++ b/README
@@ -28,7 +28,7 @@ dnf install python3-requests python3-m2crypto python3-libvirt python3-lxml pytho
 
 If you wish to test on EL 7, make that:
 
-yum install python-requests m2crypto libvirt-python python-lxml python-libguestfs pytest python-monotonic
+yum install python-requests m2crypto libvirt-python python-lxml python-libguestfs pytest python-monotonic python-mock
 
 then run the tests:
 
diff --git a/tests/guest/test_guest.py b/tests/guest/test_guest.py
index 625eb678..880807b5 100644
--- a/tests/guest/test_guest.py
+++ b/tests/guest/test_guest.py
@@ -12,6 +12,10 @@
     from io import StringIO
 import logging
 import os
+try:
+    from unittest import mock
+except ImportError:
+    import mock
 
 # Find oz library
 prefix = '.'
@@ -72,7 +76,10 @@ def setup_guest(xml, macaddress=None):
         config = configparser.ConfigParser()
         config.read_file(StringIO("[libvirt]\nuri=qemu:///session\nbridge_name=%s" % route))
 
-    guest = oz.GuestFactory.guest_factory(tdl, config, None, macaddress=macaddress)
+    # mock this - it's used in RedHatLinuxCDYumGuest._check_url() -
+    # so the tests can run without a network connection
+    with mock.patch("oz.ozutil.http_get_header", return_value={}):
+        guest = oz.GuestFactory.guest_factory(tdl, config, None, macaddress=macaddress)
     return guest
 
 tdlxml = """