diff --git a/neutron/plugins/ml2/drivers/helpers.py b/neutron/plugins/ml2/drivers/helpers.py
index 28e3320d7cb..62fcbb196d3 100644
--- a/neutron/plugins/ml2/drivers/helpers.py
+++ b/neutron/plugins/ml2/drivers/helpers.py
@@ -19,6 +19,7 @@ from oslo_config import cfg
 from oslo_db import exception as db_exc
 from oslo_log import log
 
+from neutron._i18n import _LE
 from neutron.common import exceptions as exc
 from neutron.common import utils
 from neutron.plugins.common import utils as p_utils
@@ -36,9 +37,10 @@ class BaseTypeDriver(api.TypeDriver):
     def __init__(self):
         try:
             self.physnet_mtus = utils.parse_mappings(
-                cfg.CONF.ml2.physical_network_mtus
+                cfg.CONF.ml2.physical_network_mtus, unique_values=False
             )
-        except Exception:
+        except Exception as e:
+            LOG.error(_LE("Failed to parse physical_network_mtus: %s"), e)
             self.physnet_mtus = []
 
     def get_mtu(self, physical_network=None):
diff --git a/neutron/tests/unit/plugins/ml2/drivers/test_type_flat.py b/neutron/tests/unit/plugins/ml2/drivers/test_type_flat.py
index bb3d2c7a219..302953a5dc2 100644
--- a/neutron/tests/unit/plugins/ml2/drivers/test_type_flat.py
+++ b/neutron/tests/unit/plugins/ml2/drivers/test_type_flat.py
@@ -142,6 +142,16 @@ class FlatTypeTest(testlib_api.SqlTestCase):
         self.driver.physnet_mtus = {}
         self.assertEqual(0, self.driver.get_mtu('physnet1'))
 
+    def test_parse_physical_network_mtus(self):
+        config.cfg.CONF.set_override(
+            'physical_network_mtus',
+            ['physnet1:1500', 'physnet2:1500', 'physnet3:9000'],
+            group='ml2')
+        driver = type_flat.FlatTypeDriver()
+        self.assertEqual('1500', driver.physnet_mtus['physnet1'])
+        self.assertEqual('1500', driver.physnet_mtus['physnet2'])
+        self.assertEqual('9000', driver.physnet_mtus['physnet3'])
+
 
 class FlatTypeDefaultTest(base.BaseTestCase):