diff --git a/src/react-start/index.ts b/src/react-start/index.ts
index e2aaba6e..ff809cc8 100644
--- a/src/react-start/index.ts
+++ b/src/react-start/index.ts
@@ -183,7 +183,7 @@ export const reactStartHandler = (
   const nextUrl = `${convexSiteUrl}${requestUrl.pathname}${requestUrl.search}`;
   const headers = new Headers(request.headers);
   headers.set("accept-encoding", "application/json");
-  headers.set("host", convexSiteUrl);
+  headers.set("host", new URL(convexSiteUrl).host);
   return fetch(nextUrl, {
     method: request.method,
     headers,