diff --git a/nova/compute/api.py b/nova/compute/api.py
index 70524c886cba..743630d75527 100644
--- a/nova/compute/api.py
+++ b/nova/compute/api.py
@@ -3241,13 +3241,12 @@ class API(base.Base):
         return bdms.root_bdm()
 
     def is_volume_backed_instance(self, context, instance, bdms=None):
-        if not instance.image_ref:
-            return True
-
         root_bdm = self._get_root_bdm(context, instance, bdms)
-        if not root_bdm:
-            return False
-        return root_bdm.is_volume
+        if root_bdm is not None:
+            return root_bdm.is_volume
+        # in case we hit a very old instance without root bdm, we _assume_ that
+        # instance is backed by a volume, if and only if image_ref is not set
+        return not instance.image_ref
 
     @check_instance_lock
     @check_instance_cell
diff --git a/nova/tests/unit/compute/test_compute.py b/nova/tests/unit/compute/test_compute.py
index 64b216f5c5ba..acc76d705eb3 100644
--- a/nova/tests/unit/compute/test_compute.py
+++ b/nova/tests/unit/compute/test_compute.py
@@ -8956,24 +8956,30 @@ class ComputeAPITestCase(BaseTestCase):
         self.assertIsNone(
             self.compute_api._volume_size(inst_type, blank_bdm))
 
-    def test_is_volume_backed_instance_no_image(self):
+    def test_is_volume_backed_instance_no_bdm_no_image(self):
         ctxt = self.context
 
         instance = self._create_fake_instance_obj({'image_ref': ''})
         self.assertTrue(
             self.compute_api.is_volume_backed_instance(ctxt, instance, None))
 
-    def test_is_volume_backed_instance_no_bdm(self):
+    def test_is_volume_backed_instance_empty_bdm_with_image(self):
         ctxt = self.context
-        instance = self._create_fake_instance_obj({'root_device_name': 'vda'})
+        instance = self._create_fake_instance_obj({
+            'root_device_name': 'vda',
+            'image_ref': FAKE_IMAGE_REF
+        })
         self.assertFalse(
             self.compute_api.is_volume_backed_instance(
                 ctxt, instance,
                 block_device_obj.block_device_make_list(ctxt, [])))
 
-    def test_is_volume_backed_instance_bdm_volume(self):
+    def test_is_volume_backed_instance_bdm_volume_no_image(self):
         ctxt = self.context
-        instance = self._create_fake_instance_obj({'root_device_name': 'vda'})
+        instance = self._create_fake_instance_obj({
+            'root_device_name': 'vda',
+            'image_ref': ''
+        })
         bdms = block_device_obj.block_device_make_list(ctxt,
                             [fake_block_device.FakeDbBlockDeviceDict(
                                 {'source_type': 'volume',
@@ -8985,9 +8991,14 @@ class ComputeAPITestCase(BaseTestCase):
         self.assertTrue(
             self.compute_api.is_volume_backed_instance(ctxt, instance, bdms))
 
-    def test_is_volume_backed_instance_bdm_local(self):
+    def test_is_volume_backed_instance_bdm_local_no_image(self):
+        # if the root device is local the instance is not volume backed, even
+        # if no image_ref is set.
         ctxt = self.context
-        instance = self._create_fake_instance_obj({'root_device_name': 'vda'})
+        instance = self._create_fake_instance_obj({
+            'root_device_name': 'vda',
+            'image_ref': ''
+        })
         bdms = block_device_obj.block_device_make_list(ctxt,
                [fake_block_device.FakeDbBlockDeviceDict(
                 {'source_type': 'volume',
@@ -9008,6 +9019,22 @@ class ComputeAPITestCase(BaseTestCase):
         self.assertFalse(
             self.compute_api.is_volume_backed_instance(ctxt, instance, bdms))
 
+    def test_is_volume_backed_instance_bdm_volume_with_image(self):
+        ctxt = self.context
+        instance = self._create_fake_instance_obj({
+            'root_device_name': 'vda',
+            'image_ref': FAKE_IMAGE_REF
+        })
+        bdms = block_device_obj.block_device_make_list(ctxt,
+                            [fake_block_device.FakeDbBlockDeviceDict(
+                                {'source_type': 'volume',
+                                 'device_name': '/dev/vda',
+                                 'volume_id': 'fake_volume_id',
+                                 'boot_index': 0,
+                                 'destination_type': 'volume'})])
+        self.assertTrue(
+            self.compute_api.is_volume_backed_instance(ctxt, instance, bdms))
+
     def test_is_volume_backed_instance_bdm_snapshot(self):
         ctxt = self.context
         instance = self._create_fake_instance_obj({'root_device_name': 'vda'})