diff --git a/src/NSwag.Generation.AspNetCore/Processors/OperationResponseProcessor.cs b/src/NSwag.Generation.AspNetCore/Processors/OperationResponseProcessor.cs
index d2e757388..61c9e5fba 100644
--- a/src/NSwag.Generation.AspNetCore/Processors/OperationResponseProcessor.cs
+++ b/src/NSwag.Generation.AspNetCore/Processors/OperationResponseProcessor.cs
@@ -76,7 +76,7 @@ public bool Process(OperationProcessorContext operationProcessorContext)
 
                     if (!IsVoidResponse(returnType))
                     {
-                        var returnTypeAttributes = context.MethodInfo?.ReturnParameter?.GetCustomAttributes(false).OfType<Attribute>();
+                        var returnTypeAttributes = context.MethodInfo?.ReturnParameter?.GetCustomAttributes(false).OfType<Attribute>() ?? [];
                         var contextualReturnType = returnType.ToContextualType(returnTypeAttributes);
 
                         var nullableXmlAttribute = GetResponseXmlDocsElement(context.MethodInfo, httpStatusCode)?.Attribute("nullable");