diff --git a/oslo_serialization/tests/test_yamlutils.py b/oslo_serialization/tests/test_yamlutils.py
index 817ae8c..4ba72b3 100644
--- a/oslo_serialization/tests/test_yamlutils.py
+++ b/oslo_serialization/tests/test_yamlutils.py
@@ -55,10 +55,12 @@ class BehaviorTestCase(base.BaseTestCase):
         ]
         dumped = yaml.dumps(payload)
         expected = textwrap.dedent('''\
-            - {foo: bar}
-            - {list: null}
-            - [one, two]
-            - {check: yaml, in: test}
+            - foo: bar
+            - list: null
+            - - one
+              - two
+            - check: yaml
+              in: test
         ''')
         self.assertEqual(dumped, expected)
 
diff --git a/oslo_serialization/yamlutils.py b/oslo_serialization/yamlutils.py
index 921b74e..6d6be40 100644
--- a/oslo_serialization/yamlutils.py
+++ b/oslo_serialization/yamlutils.py
@@ -67,7 +67,7 @@ def dumps(obj, is_safe=True):
             yaml_dumper = yaml.CSafeDumper
         else:
             yaml_dumper = yaml.SafeDumper
-    return yaml.dump(obj, Dumper=yaml_dumper)
+    return yaml.dump(obj, default_flow_style=False, Dumper=yaml_dumper)
 
 
 def dump(obj, fp, is_safe=True):