diff --git a/src/proxy/middleware/request/transform-outbound-payload.ts b/src/proxy/middleware/request/transform-outbound-payload.ts
index 7f416aa..a63629c 100644
--- a/src/proxy/middleware/request/transform-outbound-payload.ts
+++ b/src/proxy/middleware/request/transform-outbound-payload.ts
@@ -129,7 +129,7 @@ function openaiToAnthropic(body: any, req: Request) {
 
   const contextTokens = Number(req.promptTokens ?? 0) + Number(rest.max_tokens);
   const model =
-    contextTokens ?? 0 > CLAUDE_100K_TOKEN_THRESHOLD
+    (contextTokens ?? 0) > CLAUDE_100K_TOKEN_THRESHOLD
       ? CLAUDE_BIG
       : CLAUDE_SMALL;