diff --git a/keystone/identity/core.py b/keystone/identity/core.py
index afa397ba2f..b53d269aae 100644
--- a/keystone/identity/core.py
+++ b/keystone/identity/core.py
@@ -15,6 +15,7 @@
 """Main entry point into the Identity service."""
 
 import functools
+import itertools
 import operator
 import os
 import threading
@@ -530,15 +531,19 @@ class Manager(manager.Manager):
 
         """
         project_id = payload['resource_info']
-        try:
-            self.driver.unset_default_project_id(project_id)
-        except exception.Forbidden:
-            # NOTE(lbragstad): If the driver throws a Forbidden, it's because
-            # the driver doesn't support writes. This is the case with the
-            # in-tree LDAP implementation since it is read-only. This also
-            # ensures consistency for out-of-tree backends that might be
-            # read-only.
-            pass
+        drivers = itertools.chain(
+            self.domain_configs.values(), [{'driver': self.driver}]
+        )
+        for d in drivers:
+            try:
+                d['driver'].unset_default_project_id(project_id)
+            except exception.Forbidden:
+                # NOTE(lbragstad): If the driver throws a Forbidden, it's
+                # because the driver doesn't support writes. This is the case
+                # with the in-tree LDAP implementation since it is read-only.
+                # This also ensures consistency for out-of-tree backends that
+                # might be read-only.
+                pass
 
     # Domain ID normalization methods
     def _set_domain_id_and_mapping(self, ref, domain_id, driver,
diff --git a/keystone/tests/unit/test_backend_ldap.py b/keystone/tests/unit/test_backend_ldap.py
index a553504c7d..ddf8852a5d 100644
--- a/keystone/tests/unit/test_backend_ldap.py
+++ b/keystone/tests/unit/test_backend_ldap.py
@@ -33,6 +33,7 @@ from keystone import exception
 from keystone import identity
 from keystone.identity.backends import ldap as ldap_identity
 from keystone.identity.backends.ldap import common as common_ldap
+from keystone.identity.backends import sql as sql_identity
 from keystone.identity.mapping_backends import mapping as map
 from keystone.tests import unit
 from keystone.tests.unit.assignment import test_backends as assignment_tests
@@ -2500,6 +2501,19 @@ class MultiLDAPandSQLIdentity(BaseLDAPIdentity, unit.SQLDriverOverrides,
         base = super(BaseLDAPIdentity, self)
         base.test_remove_foreign_assignments_when_deleting_a_domain()
 
+    @mock.patch.object(ldap_identity.Identity, 'unset_default_project_id')
+    @mock.patch.object(sql_identity.Identity, 'unset_default_project_id')
+    def test_delete_project_unset_project_ids_for_all_backends(self, sql_mock,
+                                                               ldap_mock):
+        ldap_mock.side_effect = exception.Forbidden
+        project = unit.new_project_ref(
+            domain_id=CONF.identity.default_domain_id
+        )
+        project = self.resource_api.create_project(project['id'], project)
+        self.resource_api.delete_project(project['id'])
+        ldap_mock.assert_called_with(project['id'])
+        sql_mock.assert_called_with(project['id'])
+
 
 class MultiLDAPandSQLIdentityDomainConfigsInSQL(MultiLDAPandSQLIdentity):
     """Class to test the use of domain configs stored in the database.