diff --git a/src/proxy/middleware/response/streaming/transformers/anthropic-chat-to-openai.ts b/src/proxy/middleware/response/streaming/transformers/anthropic-chat-to-openai.ts
index 233677d..583477a 100644
--- a/src/proxy/middleware/response/streaming/transformers/anthropic-chat-to-openai.ts
+++ b/src/proxy/middleware/response/streaming/transformers/anthropic-chat-to-openai.ts
@@ -34,7 +34,7 @@ export const anthropicChatToOpenAI: StreamingCompletionTransformer = (
     model: params.fallbackModel,
     choices: [
       {
-        index: params.index,
+        index: 0,
         delta: { content: deltaEvent.delta.text },
         finish_reason: null,
       },