1 files changed, 1 insertions, 1 deletions
diff --git a/http/racing_server.ts b/http/racing_server.ts
index c44fc1216..0053fa428 100644
--- a/http/racing_server.ts
+++ b/http/racing_server.ts
@@ -8,7 +8,7 @@ const body = new TextEncoder().encode("Hello 1\n");
 const body4 = new TextEncoder().encode("World 4\n");
 
 function sleep(ms: number): Promise<void> {
-  return new Promise(res => setTimeout(res, ms));
+  return new Promise((res): number => setTimeout(res, ms));
 }
 
 async function delayedRespond(request: ServerRequest): Promise<void> {