Customizing icons for mapitems

[Bucky Kid]

Hello, I'm trying to distinguish icons by type within a single mapitems category.
Not using linked png file I rather want to assign the icon from external icons archive:

  <sym>bouda_m_2_4_1</sym>
  <extensions>
    <locus:icon>file:Boudy.zip:bouda_m_2_4_1.png</locus:icon>
  </extensions>

But it's not working, is Locus ignoring the element attributes for icon or is it different attribute I must set?