diff --git a/backend/package-lock.json b/backend/package-lock.json
index b06152a..5f368e3 100644
--- a/backend/package-lock.json
+++ b/backend/package-lock.json
@@ -25,6 +25,7 @@
         "@types/node": "^20.14.0",
         "@types/nodemailer": "^7.0.11",
         "@types/pg": "^8.11.6",
+        "@types/ws": "^8.18.1",
         "tsx": "^4.15.7",
         "typescript": "^5.4.5"
       }
@@ -657,6 +658,16 @@
         "pg-types": "^2.2.0"
       }
     },
+    "node_modules/@types/ws": {
+      "version": "8.18.1",
+      "resolved": "https://registry.npmjs.org/@types/ws/-/ws-8.18.1.tgz",
+      "integrity": "sha512-ThVF6DCVhA8kUGy+aazFQ4kXQ7E1Ty7A3ypFOe0IcJV8O/M511G99AW24irKrW56Wt44yG9+ij8FaqoBGkuBXg==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/node": "*"
+      }
+    },
     "node_modules/abstract-logging": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/abstract-logging/-/abstract-logging-2.0.1.tgz",
diff --git a/backend/package.json b/backend/package.json
index a963e37..892f9aa 100644
--- a/backend/package.json
+++ b/backend/package.json
@@ -26,6 +26,7 @@
     "@types/node": "^20.14.0",
     "@types/nodemailer": "^7.0.11",
     "@types/pg": "^8.11.6",
+    "@types/ws": "^8.18.1",
     "tsx": "^4.15.7",
     "typescript": "^5.4.5"
   }
diff --git a/backend/src/routes/ws.ts b/backend/src/routes/ws.ts
index 4bbcf07..1404c98 100644
--- a/backend/src/routes/ws.ts
+++ b/backend/src/routes/ws.ts
@@ -1,6 +1,6 @@
 import { FastifyPluginAsync } from 'fastify'
 import fastifyWebsocket from '@fastify/websocket'
-import type { WebSocket } from 'ws'
+import type { WebSocket, RawData } from 'ws'
 
 // hotel slug → set of connected clients
 const hotelRooms = new Map<string, Set<WebSocket>>()
@@ -18,7 +18,7 @@ const ws: FastifyPluginAsync = async (fastify) => {
       if (!hotelRooms.has(hotel)) hotelRooms.set(hotel, new Set())
       hotelRooms.get(hotel)!.add(socket)
 
-      socket.on('message', (raw) => {
+      socket.on('message', (raw: RawData) => {
         const data = raw.toString()
         const peers = hotelRooms.get(hotel)
         if (!peers) return