diff --git a/nova/api/openstack/compute/contrib/quotas.py b/nova/api/openstack/compute/contrib/quotas.py
index a0740ebe5215..dba5b49390bb 100644
--- a/nova/api/openstack/compute/contrib/quotas.py
+++ b/nova/api/openstack/compute/contrib/quotas.py
@@ -162,9 +162,9 @@ class QuotaSetsController(object):
                         raise webob.exc.HTTPBadRequest(explanation=msg)
 
             try:
-                db.quota_update(context, project_id, key, value)
-            except exception.ProjectQuotaNotFound:
                 db.quota_create(context, project_id, key, value)
+            except exception.QuotaExists:
+                db.quota_update(context, project_id, key, value)
             except exception.AdminRequired:
                 raise webob.exc.HTTPForbidden()
         return {'quota_set': self._get_quotas(context, id)}
diff --git a/nova/cmd/manage.py b/nova/cmd/manage.py
index df54e86773cd..79575fe4e804 100644
--- a/nova/cmd/manage.py
+++ b/nova/cmd/manage.py
@@ -234,9 +234,9 @@ class ProjectCommands(object):
                 if value.lower() == 'unlimited':
                     value = -1
                 try:
-                    db.quota_update(ctxt, project_id, key, value)
-                except exception.ProjectQuotaNotFound:
                     db.quota_create(ctxt, project_id, key, value)
+                except exception.QuotaExists:
+                    db.quota_update(ctxt, project_id, key, value)
             else:
                 print _('%(key)s is not a valid quota key. Valid options are: '
                         '%(options)s.') % {'key': key,
diff --git a/nova/db/sqlalchemy/api.py b/nova/db/sqlalchemy/api.py
index 5bbb21fe7904..b0b794d0d656 100644
--- a/nova/db/sqlalchemy/api.py
+++ b/nova/db/sqlalchemy/api.py
@@ -2586,7 +2586,10 @@ def quota_create(context, project_id, resource, limit):
     quota_ref.project_id = project_id
     quota_ref.resource = resource
     quota_ref.hard_limit = limit
-    quota_ref.save()
+    try:
+        quota_ref.save()
+    except db_exc.DBDuplicateEntry:
+        raise exception.QuotaExists(project_id=project_id, resource=resource)
     return quota_ref
 
 
diff --git a/nova/db/sqlalchemy/migrate_repo/versions/191_add_quota_uc.py b/nova/db/sqlalchemy/migrate_repo/versions/191_add_quota_uc.py
new file mode 100644
index 000000000000..4bc8f7e562fc
--- /dev/null
+++ b/nova/db/sqlalchemy/migrate_repo/versions/191_add_quota_uc.py
@@ -0,0 +1,40 @@
+# Copyright 2013 Mirantis Inc.
+# All Rights Reserved
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+#
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+from migrate.changeset import UniqueConstraint
+from sqlalchemy import MetaData, Table
+
+from nova.db.sqlalchemy import utils
+
+
+UC_NAME = 'uniq_quotas0project_id0resource0deleted'
+COLUMNS = ('project_id', 'resource', 'deleted')
+TABLE_NAME = 'quotas'
+
+
+def upgrade(migrate_engine):
+    meta = MetaData(bind=migrate_engine)
+    t = Table(TABLE_NAME, meta, autoload=True)
+
+    utils.drop_old_duplicate_entries_from_table(migrate_engine, TABLE_NAME,
+                                                True, *COLUMNS)
+    uc = UniqueConstraint(*COLUMNS, table=t, name=UC_NAME)
+    uc.create()
+
+
+def downgrade(migrate_engine):
+    utils.drop_unique_constraint(migrate_engine, TABLE_NAME, UC_NAME, *COLUMNS)
diff --git a/nova/db/sqlalchemy/models.py b/nova/db/sqlalchemy/models.py
index 5d9c4cbf31ac..6da9d8e19db9 100644
--- a/nova/db/sqlalchemy/models.py
+++ b/nova/db/sqlalchemy/models.py
@@ -367,7 +367,11 @@ class Quota(BASE, NovaBase):
     """
 
     __tablename__ = 'quotas'
-    __table_args__ = ()
+    __table_args__ = (
+        schema.UniqueConstraint("project_id", "resource", "deleted",
+        name="uniq_quotas0project_id0resource0deleted"
+        ),
+    )
     id = Column(Integer, primary_key=True)
 
     project_id = Column(String(255), nullable=True)
diff --git a/nova/exception.py b/nova/exception.py
index b435d85b7bb2..39028d1a87d8 100644
--- a/nova/exception.py
+++ b/nova/exception.py
@@ -704,6 +704,11 @@ class QuotaNotFound(NotFound):
     message = _("Quota could not be found")
 
 
+class QuotaExists(Duplicate):
+    message = _("Quota exists for project %(project_id)s, "
+                "resource %(resource)s")
+
+
 class QuotaResourceUnknown(QuotaNotFound):
     message = _("Unknown quota resources %(unknown)s.")
 
diff --git a/nova/tests/db/test_db_api.py b/nova/tests/db/test_db_api.py
index 85a31bc2ee91..bca5f6edb6fa 100644
--- a/nova/tests/db/test_db_api.py
+++ b/nova/tests/db/test_db_api.py
@@ -4753,6 +4753,11 @@ class QuotaTestCase(test.TestCase, ModelsObjectComparatorMixin):
         for key, value in expected.iteritems():
             self.assertEqual(value, quota_usage[key])
 
+    def test_quota_create_exists(self):
+        db.quota_create(self.ctxt, 'project1', 'resource1', 41)
+        self.assertRaises(exception.QuotaExists, db.quota_create, self.ctxt,
+                          'project1', 'resource1', 42)
+
 
 class QuotaClassTestCase(test.TestCase, ModelsObjectComparatorMixin):
 
diff --git a/nova/tests/db/test_migrations.py b/nova/tests/db/test_migrations.py
index f0c13f02995e..9e0a79161145 100644
--- a/nova/tests/db/test_migrations.py
+++ b/nova/tests/db/test_migrations.py
@@ -1699,6 +1699,36 @@ class TestNovaMigrations(BaseMigrationTestCase, CommonTestsMixIn):
                           security_groups.insert().execute,
                           dict(name='group2', project_id='fake', deleted=0))
 
+    def _pre_upgrade_191(self, engine):
+        quotas = db_utils.get_table(engine, 'quotas')
+        data = [
+            {'project_id': 'project1', 'resource': 'resource1', 'deleted': 0},
+            {'project_id': 'project1', 'resource': 'resource1', 'deleted': 0},
+            {'project_id': 'project2', 'resource': 'resource1', 'deleted': 0},
+        ]
+        for item in data:
+            quotas.insert().values(item).execute()
+        return data
+
+    def _check_191(self, engine, data):
+        quotas = db_utils.get_table(engine, 'quotas')
+
+        def get_(project_id, deleted):
+            deleted_value = 0 if not deleted else quotas.c.id
+            return quotas.select().\
+                   where(quotas.c.project_id == project_id).\
+                   where(quotas.c.deleted == deleted_value).\
+                   execute().\
+                   fetchall()
+
+        self.assertEqual(1, len(get_('project1', False)))
+        self.assertEqual(1, len(get_('project1', True)))
+        self.assertEqual(1, len(get_('project2', False)))
+        self.assertRaises(sqlalchemy.exc.IntegrityError,
+                          quotas.insert().execute,
+                          {'project_id': 'project1', 'resource': 'resource1',
+                           'deleted': 0})
+
 
 class TestBaremetalMigrations(BaseMigrationTestCase, CommonTestsMixIn):
     """Test sqlalchemy-migrate migrations."""