WhatsApp over the summer apparently refused the U.K. government’s entreaties to build what would essentially be a backdoor into its app.

The government wanted a way to tap into encrypted messages, but WhatsApp declined, according to a report by Sky News.

Terrorists have become “frequent users of encrypted apps,” creating a blind spot for law enforcement, the report cites an anonymous source in security as saying. “It is crucially important that we can access their communications – and when we can’t, it can provide a black hole for investigators.”

The summer’s request wouldn’t be the first time government officials have expressed the desired for a backdoor into WhatsApp. Following the terror attack on Parliament last March, U.K. Home Secretary Amber Rudd suggested law enforcement must be able to listen in to WhatsApp conversations, as British-born Khalid Masood, who carried out the attack, is said to have used WhatsApp moments before murdering pedestrians with his car, and stabbing an unarmed police officer to death.