diff --git a/umap/static/umap/js/modules/sync/engine.js b/umap/static/umap/js/modules/sync/engine.js
index 640ae5f4..bc640aa2 100644
--- a/umap/static/umap/js/modules/sync/engine.js
+++ b/umap/static/umap/js/modules/sync/engine.js
@@ -75,19 +75,20 @@ export class SyncEngine {
       this.reconnect()
       return
     }
-    this.start(response.token)
+    await this.start(response.token)
   }
 
-  start(authToken) {
+  async start(authToken) {
     const path = this._umap.urls.get('ws_sync', { map_id: this._umap.id })
     const protocol = window.location.protocol === 'http:' ? 'ws:' : 'wss:'
-    this.transport = new WebSocketTransport(
+    this.transport = new WebSocketTransport(this)
+    await this.transport.connect(
       `${protocol}//${window.location.host}${path}`,
       authToken,
-      this,
       this.peerId,
       this._umap.properties.user?.name
     )
+    this.onConnection()
   }
 
   stop() {
@@ -108,11 +109,11 @@ export class SyncEngine {
     this.websocketConnected = false
     this.updaters.map.update({ key: 'numberOfConnectedPeers' })
 
-    this._reconnectTimeout = setTimeout(() => {
+    this._reconnectTimeout = setTimeout(async () => {
       if (this._reconnectDelay < MAX_RECONNECT_DELAY) {
         this._reconnectDelay = this._reconnectDelay * RECONNECT_DELAY_FACTOR
       }
-      this.authenticate()
+      await this.authenticate()
     }, this._reconnectDelay)
   }
   upsert(subject, metadata, value) {
diff --git a/umap/static/umap/js/modules/sync/websocket.js b/umap/static/umap/js/modules/sync/websocket.js
index 5a18f880..ee51019a 100644
--- a/umap/static/umap/js/modules/sync/websocket.js
+++ b/umap/static/umap/js/modules/sync/websocket.js
@@ -3,53 +3,57 @@ const PING_INTERVAL = 30000
 const FIRST_CONNECTION_TIMEOUT = 2000
 
 export class WebSocketTransport {
-  constructor(webSocketURI, authToken, messagesReceiver, peerId, username) {
+  constructor(messagesReceiver) {
     this.receiver = messagesReceiver
+  }
 
-    this.websocket = new WebSocket(webSocketURI)
+  async connect(webSocketURI, authToken, peerId, username) {
+    return new Promise((resolve, reject) => {
+      this.websocket = new WebSocket(webSocketURI)
 
-    this.websocket.onopen = () => {
-      this.send('JoinRequest', { token: authToken, peer: peerId, username })
-      this.receiver.onConnection()
-    }
-    this.websocket.addEventListener('message', this.onMessage.bind(this))
-    this.websocket.onclose = () => {
-      console.log('websocket closed')
-      if (!this.receiver.closeRequested) {
-        console.log('Not requested, reconnecting...')
-        this.receiver.reconnect()
+      this.websocket.onopen = () => {
+        this.send('JoinRequest', { token: authToken, peer: peerId, username })
+        resolve(this.websocket)
       }
-    }
-
-    this.websocket.onerror = (error) => {
-      console.log('WS ERROR', error)
-    }
-
-    this.ensureOpen = setInterval(() => {
-      if (this.websocket.readyState !== WebSocket.OPEN) {
-        this.websocket.close()
-        clearInterval(this.ensureOpen)
+      this.websocket.addEventListener('message', this.onMessage.bind(this))
+      this.websocket.onclose = () => {
+        console.log('websocket closed')
+        if (!this.receiver.closeRequested) {
+          console.log('Not requested, reconnecting...')
+          this.receiver.reconnect()
+        }
       }
-    }, FIRST_CONNECTION_TIMEOUT)
 
-    // To ensure the connection is still alive, we send ping and expect pong back.
-    // Websocket provides a `ping` method to keep the connection alive, but it's
-    // unfortunately not possible to access it from the WebSocket object.
-    // See https://making.close.com/posts/reliable-websockets/ for more details.
-    this.pingInterval = setInterval(() => {
-      if (this.websocket.readyState === WebSocket.OPEN) {
-        console.log('sending ping')
-        this.websocket.send('ping')
-        this.pongReceived = false
-        setTimeout(() => {
-          if (!this.pongReceived) {
-            console.warn('No pong received, reconnecting...')
-            this.websocket.close()
-            clearInterval(this.pingInterval)
-          }
-        }, PONG_TIMEOUT)
+      this.websocket.onerror = (error) => {
+        console.log('WS ERROR', error)
       }
-    }, PING_INTERVAL)
+
+      this.ensureOpen = setInterval(() => {
+        if (this.websocket.readyState !== WebSocket.OPEN) {
+          this.websocket.close()
+          clearInterval(this.ensureOpen)
+        }
+      }, FIRST_CONNECTION_TIMEOUT)
+
+      // To ensure the connection is still alive, we send ping and expect pong back.
+      // Websocket provides a `ping` method to keep the connection alive, but it's
+      // unfortunately not possible to access it from the WebSocket object.
+      // See https://making.close.com/posts/reliable-websockets/ for more details.
+      this.pingInterval = setInterval(() => {
+        if (this.websocket.readyState === WebSocket.OPEN) {
+          console.log('sending ping')
+          this.websocket.send('ping')
+          this.pongReceived = false
+          setTimeout(() => {
+            if (!this.pongReceived) {
+              console.warn('No pong received, reconnecting...')
+              this.websocket.close()
+              clearInterval(this.pingInterval)
+            }
+          }, PONG_TIMEOUT)
+        }
+      }, PING_INTERVAL)
+    })
   }
 
   onMessage(wsMessage) {