Icon not updating for Safari push notifications

Hello,

We've changed logotype and are having issues in macOS replacing our old web push-notification icon with the new one.

We've spoken to Airship whom we are partnering with and have received the information that it's up to the browser to decide when it wants to update its icon. 

Is there any way we can somehow force the browser to fetch our new icon/logotype? If not, how long would it typically take until it's updated?
Unfortunately, the logo can not be updated after the user has already subscribed. Existing subscribers would need to fully clear their browser stored content including existing push subscriptions, and then opt-in to notifications again.
Icon not updating for Safari push notifications
 
 
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