diff --git a/lib/helper/Playwright.js b/lib/helper/Playwright.js
index 8e68fc74d..a0a872ea8 100644
--- a/lib/helper/Playwright.js
+++ b/lib/helper/Playwright.js
@@ -3435,7 +3435,7 @@ class Playwright extends Helper {
   }
 
   _logWebsocketMessages(message) {
-    this.webSocketMessages += message
+    this.webSocketMessages.push(message)
   }
 }
 
diff --git a/lib/helper/Puppeteer.js b/lib/helper/Puppeteer.js
index 0c219144e..9bc82b69d 100644
--- a/lib/helper/Puppeteer.js
+++ b/lib/helper/Puppeteer.js
@@ -2772,7 +2772,7 @@ class Puppeteer extends Helper {
   }
 
   _logWebsocketMessages(message) {
-    this.webSocketMessages += message
+    this.webSocketMessages.push(message)
   }
 }