diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 99a781b782..46eafb7bbc 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -5544,13 +5544,14 @@ class ComputeManager(manager.Manager):
         if CONF.volume_usage_poll_interval <= 0:
             return
 
-        vol_stats = []
         mp = bdm.device_name
         # Handle bootable volumes which will not contain /dev/
         if '/dev/' in mp:
             mp = mp[5:]
         try:
             vol_stats = self.driver.block_stats(instance, mp)
+            if vol_stats is None:
+                return
         except NotImplementedError:
             return
 
diff --git a/nova/tests/unit/compute/test_compute_mgr.py b/nova/tests/unit/compute/test_compute_mgr.py
index 232a952450..54599967ff 100644
--- a/nova/tests/unit/compute/test_compute_mgr.py
+++ b/nova/tests/unit/compute/test_compute_mgr.py
@@ -4931,6 +4931,23 @@ class ComputeManagerUnitTestCase(test.NoDBTestCase):
             expected_reqspec_hints, self.compute._get_scheduler_hints(
                 filter_properties, reqspec))
 
+    def test_notify_volume_usage_detach_no_block_stats(self):
+        """Tests the case that the virt driver returns None from the
+        block_stats() method and no notification is sent, similar to the
+        virt driver raising NotImplementedError.
+        """
+        self.flags(volume_usage_poll_interval=60)
+        fake_instance = objects.Instance()
+        fake_bdm = objects.BlockDeviceMapping(device_name='/dev/vda')
+        with mock.patch.object(self.compute.driver, 'block_stats',
+                               return_value=None) as block_stats:
+            # Assert a notification isn't sent.
+            with mock.patch.object(self.compute.notifier, 'info',
+                                   new_callable=mock.NonCallableMock):
+                self.compute._notify_volume_usage_detach(
+                    self.context, fake_instance, fake_bdm)
+        block_stats.assert_called_once_with(fake_instance, 'vda')
+
 
 class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
     def setUp(self):
diff --git a/nova/virt/driver.py b/nova/virt/driver.py
index 2cbd63d0a1..83b6eee522 100644
--- a/nova/virt/driver.py
+++ b/nova/virt/driver.py
@@ -1400,6 +1400,13 @@ class ComputeDriver(object):
         unused.
 
         Note that this function takes an instance ID.
+
+        :param instance: nova.objects.Instance to get block storage statistics
+        :param disk_id: mountpoint name, e.g. "vda"
+        :returns: None if block statistics could not be retrieved, otherwise a
+            list of the form: [rd_req, rd_bytes, wr_req, wr_bytes, errs]
+        :raises: NotImplementedError if the driver does not implement this
+            method
         """
         raise NotImplementedError()