diff --git a/swift/common/ring/builder.py b/swift/common/ring/builder.py
index 43185789a6..1ac41594c5 100644
--- a/swift/common/ring/builder.py
+++ b/swift/common/ring/builder.py
@@ -937,6 +937,8 @@ class RingBuilder(object):
 
         Deliberately includes duplicates.
         """
+        if self._replica2part2dev is None:
+            return []
         return [self.devs[part2dev[part]]
                 for part2dev in self._replica2part2dev
                 if part < len(part2dev)]
diff --git a/test/unit/common/ring/test_builder.py b/test/unit/common/ring/test_builder.py
index 5a1d4faf10..d9007fb5ba 100644
--- a/test/unit/common/ring/test_builder.py
+++ b/test/unit/common/ring/test_builder.py
@@ -797,6 +797,8 @@ class TestRingBuilder(unittest.TestCase):
 
     def test_get_part_devices(self):
         rb = ring.RingBuilder(8, 3, 1)
+        self.assertEqual(rb.get_part_devices(0), [])
+
         rb.add_dev({'id': 0, 'region': 0, 'zone': 0, 'weight': 1,
                     'ip': '127.0.0.1', 'port': 10000, 'device': 'sda1'})
         rb.add_dev({'id': 1, 'region': 0, 'zone': 1, 'weight': 1,