diff --git a/src/server/proxy.ts b/src/server/proxy.ts
index 3fd8c15..fbe522b 100644
--- a/src/server/proxy.ts
+++ b/src/server/proxy.ts
@@ -9,6 +9,7 @@ const upstreams = new Map<ServerWebSocket<WsData>, WebSocket>()
 interface WsData {
   port: number
   path: string
+  protocols: string[]
 }
 
 export function extractSubdomain(host: string): string | null {
@@ -73,8 +74,13 @@ export function proxyWebSocket(subdomain: string, req: Request, server: Server<W
 
   const url = new URL(req.url)
   const path = url.pathname + url.search
+  const protocolHeader = req.headers.get('sec-websocket-protocol')
+  const protocols = protocolHeader ? protocolHeader.split(',').map(p => p.trim()) : []
 
-  const ok = server.upgrade(req, { data: { port: app.port, path } as WsData })
+  const headers: Record<string, string> = {}
+  if (protocolHeader) headers['sec-websocket-protocol'] = protocolHeader
+
+  const ok = server.upgrade(req, { data: { port: app.port, path, protocols } as WsData, headers })
   if (ok) return undefined
   return new Response('WebSocket upgrade failed', { status: 500 })
 }
@@ -82,7 +88,7 @@ export function proxyWebSocket(subdomain: string, req: Request, server: Server<W
 export const websocket = {
   open(ws: ServerWebSocket<WsData>) {
     const { port, path } = ws.data
-    const upstream = new WebSocket(`ws://localhost:${port}${path}`)
+    const upstream = new WebSocket(`ws://localhost:${port}${path}`, ws.data.protocols)
 
     upstream.binaryType = 'arraybuffer'
     upstreams.set(ws, upstream)