diff --git a/tests/basic/test_reasoning.py b/tests/basic/test_reasoning.py
index b13e02cd4..0386f29bc 100644
--- a/tests/basic/test_reasoning.py
+++ b/tests/basic/test_reasoning.py
@@ -424,6 +424,7 @@ End"""
                 self.choices[0].message.reasoning = (
                     reasoning  # Using reasoning instead of reasoning_content
                 )
+                delattr(self.choices[0].message, "reasoning_content")
                 self.finish_reason = "stop"
 
         mock_completion = MockCompletion(main_content, reasoning_content)