diff --git a/nova/compute/api.py b/nova/compute/api.py
index 9bacd6b998a..c924378093a 100644
--- a/nova/compute/api.py
+++ b/nova/compute/api.py
@@ -1541,7 +1541,7 @@ def _confirm_resize_on_deleting(self, context, instance):
             LOG.info(_('Migration %s may have been confirmed during delete') %
                     migration.id, context=context, instance=instance)
             return
-        quotas = self._reserve_quota_delta(context, deltas)
+        quotas = self._reserve_quota_delta(context, deltas, instance)
 
         self._record_action_start(context, instance,
                                   instance_actions.CONFIRM_RESIZE)
@@ -2173,7 +2173,7 @@ def revert_resize(self, context, instance):
 
         # reverse quota reservation for increased resource usage
         deltas = self._reverse_upsize_quota_delta(context, migration)
-        quotas = self._reserve_quota_delta(context, deltas)
+        quotas = self._reserve_quota_delta(context, deltas, instance)
 
         instance.task_state = task_states.RESIZE_REVERTING
         try:
@@ -2210,7 +2210,7 @@ def confirm_resize(self, context, instance, migration=None):
 
         # reserve quota only for any decrease in resource usage
         deltas = self._downsize_quota_delta(context, instance)
-        quotas = self._reserve_quota_delta(context, deltas)
+        quotas = self._reserve_quota_delta(context, deltas, instance)
 
         migration.status = 'confirming'
         migration.save()
@@ -2282,20 +2282,22 @@ def _downsize_quota_delta(context, instance):
         return API._resize_quota_delta(context, new_flavor, old_flavor, 1, -1)
 
     @staticmethod
-    def _reserve_quota_delta(context, deltas, project_id=None):
+    def _reserve_quota_delta(context, deltas, instance):
         """If there are deltas to reserve, construct a Quotas object and
         reserve the deltas for the given project.
 
         @param context:    The nova request context.
         @param deltas:     A dictionary of the proposed delta changes.
-        @param project_id: Specify the project_id if current context
-                           is admin and admin wants to impact on
-                           common user's tenant.
+        @param instance:   The instance we're operating on, so that
+                           quotas can use the correct project_id/user_id.
         @return: nova.objects.quotas.Quotas
         """
         quotas = quotas_obj.Quotas()
         if deltas:
-            quotas.reserve(context, project_id=project_id, **deltas)
+            project_id, user_id = quotas_obj.ids_from_instance(context,
+                                                               instance)
+            quotas.reserve(context, project_id=project_id, user_id=user_id,
+                           **deltas)
         return quotas
 
     @staticmethod
@@ -2370,10 +2372,7 @@ def resize(self, context, instance, flavor_id=None,
         deltas = self._upsize_quota_delta(context, new_instance_type,
                                           current_instance_type)
         try:
-            project_id, user_id = quotas_obj.ids_from_instance(context,
-                                                               instance)
-            quotas = self._reserve_quota_delta(context, deltas,
-                                               project_id=project_id)
+            quotas = self._reserve_quota_delta(context, deltas, instance)
         except exception.OverQuota as exc:
             quotas = exc.kwargs['quotas']
             overs = exc.kwargs['overs']
diff --git a/nova/tests/compute/test_compute_api.py b/nova/tests/compute/test_compute_api.py
index f4d954d031d..200db8a919e 100644
--- a/nova/tests/compute/test_compute_api.py
+++ b/nova/tests/compute/test_compute_api.py
@@ -426,7 +426,7 @@ def _test_delete_resized_part(self, inst):
                                                ).AndReturn('deltas')
         fake_quotas = quotas_obj.Quotas.from_reservations(self.context,
                                                           ['rsvs'])
-        self.compute_api._reserve_quota_delta(self.context, 'deltas'
+        self.compute_api._reserve_quota_delta(self.context, 'deltas', inst,
                                               ).AndReturn(fake_quotas)
         self.compute_api._record_action_start(
             self.context, inst, instance_actions.CONFIRM_RESIZE)
@@ -809,8 +809,8 @@ def _test_confirm_resize(self, mig_ref_passed=False):
         resvs = ['resvs']
         fake_quotas = quotas_obj.Quotas.from_reservations(self.context, resvs)
 
-        self.compute_api._reserve_quota_delta(self.context,
-                                              'deltas').AndReturn(fake_quotas)
+        self.compute_api._reserve_quota_delta(self.context, 'deltas',
+                                              fake_inst).AndReturn(fake_quotas)
 
         def _check_mig(expected_task_state=None):
             self.assertEqual('confirming', fake_mig.status)
@@ -870,8 +870,8 @@ def _test_revert_resize(self):
         resvs = ['resvs']
         fake_quotas = quotas_obj.Quotas.from_reservations(self.context, resvs)
 
-        self.compute_api._reserve_quota_delta(self.context,
-                                              'deltas').AndReturn(fake_quotas)
+        self.compute_api._reserve_quota_delta(self.context, 'deltas',
+                                              fake_inst).AndReturn(fake_quotas)
 
         def _check_state(expected_task_state=None):
             self.assertEqual(task_states.RESIZE_REVERTING,
@@ -927,7 +927,7 @@ def test_revert_resize_concurent_fail(self):
         resvs = ['resvs']
         fake_quotas = quotas_obj.Quotas.from_reservations(self.context, resvs)
         self.compute_api._reserve_quota_delta(
-            self.context, delta).AndReturn(fake_quotas)
+            self.context, delta, fake_inst).AndReturn(fake_quotas)
 
         exc = exception.UnexpectedTaskStateError(
             actual=task_states.RESIZE_REVERTING, expected=None)
@@ -992,7 +992,7 @@ def _test_resize(self, flavor_id_passed=True,
                     self.context, new_flavor,
                     current_flavor).AndReturn('deltas')
             self.compute_api._reserve_quota_delta(self.context, 'deltas',
-                    project_id=project_id).AndReturn(fake_quotas)
+                    fake_inst).AndReturn(fake_quotas)
 
             def _check_state(expected_task_state=None):
                 self.assertEqual(task_states.RESIZE_PREP,
@@ -1166,7 +1166,7 @@ def test_resize_quota_exceeds_fails(self):
                                headroom=headroom)
 
         self.compute_api._reserve_quota_delta(self.context, deltas,
-                project_id=fake_inst['project_id']).AndRaise(
+                fake_inst).AndRaise(
                         exception.OverQuota(**over_quota_args))
 
         self.mox.ReplayAll()