diff --git a/python/sglang/bench_serving.py b/python/sglang/bench_serving.py
index 036d1e864..9887c7161 100644
--- a/python/sglang/bench_serving.py
+++ b/python/sglang/bench_serving.py
@@ -128,7 +128,7 @@ async def async_request_trt_llm(
                         timestamp = time.perf_counter()
                         # First token
                         if ttft == 0.0:
-                            ttft = time.perf_counter() - st
+                            ttft = timestamp - st
                             output.ttft = ttft
 
                         # Decoding phase