diff --git a/wp-includes/js/backbone.js b/wp-includes/js/backbone.js
index 3e09d0dcb0..e55eacbf23 100644
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374 | 374 | // Cleans up memory bindings between the listener and the listenee. |
375 | 375 | Listening.prototype.cleanup = function() { |
376 | 376 | delete this.listener._listeningTo[this.obj._listenId]; |
377 | | if (!this.interop) delete this.obj._listeners[this.id]; |
| 377 | if (!this.interop && this.obj._listeners) delete this.obj._listeners[this.id]; |
378 | 378 | }; |
379 | 379 | |
380 | 380 | // Aliases for backwards compatibility. |