diff --git a/vllm/entrypoints/openai/protocol.py b/vllm/entrypoints/openai/protocol.py
index a96ca1f75700..032dc49d16de 100644
--- a/vllm/entrypoints/openai/protocol.py
+++ b/vllm/entrypoints/openai/protocol.py
@@ -1238,6 +1238,9 @@ class ChatCompletionLogProb(OpenAIBaseModel):
 
 
 class ChatCompletionLogProbsContent(ChatCompletionLogProb):
+    # Workaround: redefine fields name cache so that it's not
+    # shared with the super class.
+    field_names: ClassVar[Optional[set[str]]] = None
     top_logprobs: list[ChatCompletionLogProb] = Field(default_factory=list)