diff --git a/oslo_versionedobjects/fields.py b/oslo_versionedobjects/fields.py
index 670f911d..edda623d 100644
--- a/oslo_versionedobjects/fields.py
+++ b/oslo_versionedobjects/fields.py
@@ -293,7 +293,7 @@ class Enum(String):
 
     @property
     def valid_values(self):
-        return tuple(self._valid_values)
+        return copy.copy(self._valid_values)
 
     def coerce(self, obj, attr, value):
         if value not in self._valid_values:
diff --git a/oslo_versionedobjects/tests/test_fields.py b/oslo_versionedobjects/tests/test_fields.py
index 4479bf01..7eb17a97 100644
--- a/oslo_versionedobjects/tests/test_fields.py
+++ b/oslo_versionedobjects/tests/test_fields.py
@@ -55,7 +55,7 @@ class FakeEnumAlt(fields.Enum):
     PLATYPUS = "platypus"
     AARDVARK = "aardvark"
 
-    ALL = (FROG, PLATYPUS, AARDVARK)
+    ALL = set([FROG, PLATYPUS, AARDVARK])
 
     def __init__(self, **kwargs):
         super(FakeEnumAlt, self).__init__(valid_values=FakeEnumAlt.ALL,
@@ -256,6 +256,10 @@ class TestBaseEnum(TestField):
         self.assertEqual(self.field.valid_values,
                          FakeEnum.ALL)
 
+    def test_valid_values_keeps_type(self):
+        self.assertIsInstance(self.field.valid_values, tuple)
+        self.assertIsInstance(FakeEnumAltField().valid_values, set)
+
 
 class TestEnum(TestField):
     def setUp(self):