Intercom does not work on softphone

[Colin911]

I have set up intercom to work. If I dial my paging number (set at *9 in my config) and an extension that is on a desktop phone, the intercom works fine. But if I dial an extension hooked up to a softphone (browser extension) the recipient just rings and has to pick up. Is there a way to fix this or is this by design for some reason?