diff --git a/rest_framework/schemas/openapi.py b/rest_framework/schemas/openapi.py
index ac846bf80..801169eb4 100644
--- a/rest_framework/schemas/openapi.py
+++ b/rest_framework/schemas/openapi.py
@@ -462,7 +462,7 @@ class AutoSchema(ViewInspector):
 
         content = self._map_serializer(serializer)
         # No required fields for PATCH
-        if method == 'PATCH':
+        if method == 'PATCH' and content.get('required'):
             del content['required']
         # No read_only fields for request.
         for name, schema in content['properties'].copy().items():