diff --git a/openstack_virtual_baremetal/build_nodes_json.py b/openstack_virtual_baremetal/build_nodes_json.py
index f02b994..452afc3 100755
--- a/openstack_virtual_baremetal/build_nodes_json.py
+++ b/openstack_virtual_baremetal/build_nodes_json.py
@@ -164,6 +164,14 @@ def _build_nodes(nova, glance, bmc_ports, bm_ports, provision_net,
             image = cache.get(baremetal.image['id'])
             if image.get('hw_firmware_type') == 'uefi':
                 node['capabilities'] += ",boot_mode:uefi"
+        else:
+            # With boot from volume the flavor disk size doesn't matter.  We
+            # need to look up the volume disk size.
+            cloud = os.environ.get('OS_CLOUD')
+            cinder = os_client_config.make_client('volume', cloud=cloud)
+            vol_id = baremetal.to_dict()['os-extended-volumes:volumes_attached'][0]['id']
+            volume = cinder.volumes.get(vol_id)
+            node['disk'] = volume.size
 
         bm_name_end = baremetal.name[len(baremetal_base):]
         if '-' in bm_name_end:
diff --git a/openstack_virtual_baremetal/tests/test_build_nodes_json.py b/openstack_virtual_baremetal/tests/test_build_nodes_json.py
index 5f84d55..07a5ec0 100644
--- a/openstack_virtual_baremetal/tests/test_build_nodes_json.py
+++ b/openstack_virtual_baremetal/tests/test_build_nodes_json.py
@@ -262,7 +262,8 @@ class TestBuildNodesJson(testtools.TestCase):
         mock_flavor.disk = 1024
         nova.flavors.get.return_value = mock_flavor
 
-    def test_build_nodes(self):
+    @mock.patch('os_client_config.make_client')
+    def test_build_nodes(self, mock_make_client):
         bmc_ports = [{'fixed_ips': [{'ip_address': '1.1.1.1'}]},
                      {'fixed_ips': [{'ip_address': '1.1.1.2'}]}
                      ]
@@ -270,6 +271,15 @@ class TestBuildNodesJson(testtools.TestCase):
         nova = mock.Mock()
         servers = [mock.Mock(), mock.Mock(), mock.Mock()]
         self._create_build_nodes_mocks(nova, servers)
+        servers[1].image = None
+        mock_to_dict = {'os-extended-volumes:volumes_attached':
+                            [{'id': 'v0lume'}]}
+        servers[1].to_dict.return_value = mock_to_dict
+        mock_cinder = mock.Mock()
+        mock_make_client.return_value = mock_cinder
+        mock_vol = mock.Mock()
+        mock_vol.size = 100
+        mock_cinder.volumes.get.return_value = mock_vol
         servers[2].name = 'undercloud'
         servers[2].flavor = {'id': '1'}
         servers[2].addresses = {'provision': [{'OS-EXT-IPS-MAC:mac_addr':
@@ -286,7 +296,8 @@ class TestBuildNodesJson(testtools.TestCase):
          extra_nodes,
          network_details) = build_nodes_json._build_nodes(
             nova, glance, bmc_ports, bm_ports, 'provision', 'bm', 'undercloud')
-        expected_nodes = TEST_NODES
+        expected_nodes = copy.deepcopy(TEST_NODES)
+        expected_nodes[1]['disk'] = 100
         self.assertEqual(expected_nodes, nodes)
         self.assertEqual([('1.1.1.1', 'bm_0'), ('1.1.1.2', 'bm_1')],
                          bmc_bm_pairs)