How to change favicon on SharePoint Online public site

Hi,

I'm Office 365 E3 user and would like to know if it's possible to change custom favicon (the tiny icon of the webpage appeared on the tab of the browser) on my public site on SharePoint Online.

I have tried to change the URL <!--SPM:<SharePoint:SPShortcutIcon runat="server" IconUrl="https://ixi-public.sharepoint.com/SiteAssets/favicon.ico"/>--> from my masterpage .html file but IT'S ONLY WORKING WHEN I'M SIGNED IN, otherwise it shows the default sharepoint favicon again.

Thanks.

Cheers, IXI solution