diff --git a/dom/push/test/xpcshell/head.js b/dom/push/test/xpcshell/head.js
index 71070ca2d46f..96c856f7ea7e 100644
--- a/dom/push/test/xpcshell/head.js
+++ b/dom/push/test/xpcshell/head.js
@@ -187,6 +187,7 @@ function MockWebSocket(originalURI, handlers = {}) {
   this._onUnregister = handlers.onUnregister;
   this._onACK = handlers.onACK;
   this._onPing = handlers.onPing;
+  this._onBroadcastSubscribe = handlers.onBroadcastSubscribe;
 }
 
 MockWebSocket.prototype = {
@@ -259,6 +260,13 @@ MockWebSocket.prototype = {
       }
       break;
 
+    case 'broadcast_subscribe':
+      if (typeof this._onBroadcastSubscribe != 'function') {
+        throw new Error('Unexpected broadcast_subscribe');
+      }
+      this._onBroadcastSubscribe(request);
+      break;
+
     default:
       throw new Error('Unexpected message: ' + messageType);
     }