diff --git a/nova/tests/unit/virt/libvirt/test_blockinfo.py b/nova/tests/unit/virt/libvirt/test_blockinfo.py
index 0116620fb66e..54540d33123f 100644
--- a/nova/tests/unit/virt/libvirt/test_blockinfo.py
+++ b/nova/tests/unit/virt/libvirt/test_blockinfo.py
@@ -868,6 +868,26 @@ class LibvirtBlockInfoTest(test.NoDBTestCase):
                                 'virtio', 'ide', root_device_name='/dev/vda')
         mock_get_bus.assert_called_once_with('kvm', '/dev/vda')
 
+    @mock.patch('nova.virt.libvirt.blockinfo.find_disk_dev_for_disk_bus',
+                return_value='vda')
+    @mock.patch('nova.virt.libvirt.blockinfo.get_disk_bus_for_disk_dev',
+                return_value='virtio')
+    def test_get_root_info_no_bdm_empty_image_meta(self, mock_get_bus,
+                                                   mock_find_dev):
+        # The evacuate operation passes image_ref=None to the compute node for
+        # rebuild which then defaults image_meta to {}, so we don't have any
+        # attributes in the ImageMeta object passed to get_root_info and we
+        # need to make sure we don't try lazy-loading anything.
+        instance = objects.Instance(**self.test_instance)
+        image_meta = objects.ImageMeta.from_dict({})
+        blockinfo.get_root_info(instance, 'kvm', image_meta, None,
+                                'virtio', 'ide')
+        mock_find_dev.assert_called_once_with({}, 'virtio')
+
+        blockinfo.get_root_info(instance, 'kvm', image_meta, None,
+                                'virtio', 'ide', root_device_name='/dev/vda')
+        mock_get_bus.assert_called_once_with('kvm', '/dev/vda')
+
     @mock.patch('nova.virt.libvirt.blockinfo.get_info_from_bdm')
     def test_get_root_info_bdm(self, mock_get_info):
         instance = objects.Instance(**self.test_instance)
diff --git a/nova/virt/libvirt/blockinfo.py b/nova/virt/libvirt/blockinfo.py
index 28390c658f87..f0012e6d8a73 100644
--- a/nova/virt/libvirt/blockinfo.py
+++ b/nova/virt/libvirt/blockinfo.py
@@ -429,7 +429,11 @@ def get_root_info(instance, virt_type, image_meta, root_bdm,
         root_bdm.get('source_type') == 'image' and
         root_bdm.get('destination_type') == 'local'))
     if no_root_bdm:
-        if image_meta.disk_format == 'iso':
+        # NOTE(mriedem): In case the image_meta object was constructed from
+        # an empty dict, like in the case of evacuate, we have to first check
+        # if disk_format is set on the ImageMeta object.
+        if (image_meta.obj_attr_is_set('disk_format') and
+                image_meta.disk_format == 'iso'):
             root_device_bus = cdrom_bus
             root_device_type = 'cdrom'
         else: