diff --git a/tests/serializers/test_yaml.py b/tests/serializers/test_yaml.py
index e876597e9d..dbcbd57003 100644
--- a/tests/serializers/test_yaml.py
+++ b/tests/serializers/test_yaml.py
@@ -115,7 +115,9 @@ class YamlSerializerTestCase(SerializersTestBase, TestCase):
     author: %(author_pk)s
     headline: Poker has no place on ESPN
     pub_date: 2006-06-16 11:00:00
-    categories: [%(first_category_pk)s, %(second_category_pk)s]
+    categories:""" + (
+        ' [%(first_category_pk)s, %(second_category_pk)s]' if yaml.__version__ < '5.1'
+        else '\n    - %(first_category_pk)s\n    - %(second_category_pk)s') + """
     meta_data: []
 """
 
diff --git a/tests/timezones/tests.py b/tests/timezones/tests.py
index e54b011c04..7a63bac670 100644
--- a/tests/timezones/tests.py
+++ b/tests/timezones/tests.py
@@ -643,7 +643,7 @@ class SerializationTests(SimpleTestCase):
         self.assertEqual(obj.dt, dt)
 
         if not isinstance(serializers.get_serializer('yaml'), serializers.BadSerializer):
-            data = serializers.serialize('yaml', [Event(dt=dt)])
+            data = serializers.serialize('yaml', [Event(dt=dt)], default_flow_style=None)
             self.assert_yaml_contains_datetime(data, "2011-09-01 13:20:30")
             obj = next(serializers.deserialize('yaml', data)).object
             self.assertEqual(obj.dt, dt)
@@ -667,7 +667,7 @@ class SerializationTests(SimpleTestCase):
         self.assertEqual(obj.dt, dt)
 
         if not isinstance(serializers.get_serializer('yaml'), serializers.BadSerializer):
-            data = serializers.serialize('yaml', [Event(dt=dt)])
+            data = serializers.serialize('yaml', [Event(dt=dt)], default_flow_style=None)
             self.assert_yaml_contains_datetime(data, "2011-09-01 13:20:30.405060")
             obj = next(serializers.deserialize('yaml', data)).object
             self.assertEqual(obj.dt, dt)
@@ -691,7 +691,7 @@ class SerializationTests(SimpleTestCase):
         self.assertEqual(obj.dt, dt)
 
         if not isinstance(serializers.get_serializer('yaml'), serializers.BadSerializer):
-            data = serializers.serialize('yaml', [Event(dt=dt)])
+            data = serializers.serialize('yaml', [Event(dt=dt)], default_flow_style=None)
             self.assert_yaml_contains_datetime(data, "2011-09-01 17:20:30.405060+07:00")
             obj = next(serializers.deserialize('yaml', data)).object
             self.assertEqual(obj.dt.replace(tzinfo=UTC), dt)
@@ -715,7 +715,7 @@ class SerializationTests(SimpleTestCase):
         self.assertEqual(obj.dt, dt)
 
         if not isinstance(serializers.get_serializer('yaml'), serializers.BadSerializer):
-            data = serializers.serialize('yaml', [Event(dt=dt)])
+            data = serializers.serialize('yaml', [Event(dt=dt)], default_flow_style=None)
             self.assert_yaml_contains_datetime(data, "2011-09-01 10:20:30+00:00")
             obj = next(serializers.deserialize('yaml', data)).object
             self.assertEqual(obj.dt.replace(tzinfo=UTC), dt)
@@ -739,7 +739,7 @@ class SerializationTests(SimpleTestCase):
         self.assertEqual(obj.dt, dt)
 
         if not isinstance(serializers.get_serializer('yaml'), serializers.BadSerializer):
-            data = serializers.serialize('yaml', [Event(dt=dt)])
+            data = serializers.serialize('yaml', [Event(dt=dt)], default_flow_style=None)
             self.assert_yaml_contains_datetime(data, "2011-09-01 13:20:30+03:00")
             obj = next(serializers.deserialize('yaml', data)).object
             self.assertEqual(obj.dt.replace(tzinfo=UTC), dt)
@@ -763,7 +763,7 @@ class SerializationTests(SimpleTestCase):
         self.assertEqual(obj.dt, dt)
 
         if not isinstance(serializers.get_serializer('yaml'), serializers.BadSerializer):
-            data = serializers.serialize('yaml', [Event(dt=dt)])
+            data = serializers.serialize('yaml', [Event(dt=dt)], default_flow_style=None)
             self.assert_yaml_contains_datetime(data, "2011-09-01 17:20:30+07:00")
             obj = next(serializers.deserialize('yaml', data)).object
             self.assertEqual(obj.dt.replace(tzinfo=UTC), dt)