libxfce4menu icon names limitation

[Martin Kraus]

hello,
  surprisingly, i'm still fighting the menu system:( I've got a question. Is
there any limitation to what names can be used in the .directory icon names?
I'm trying to include an icon for debian generated menu.

I named the icon "system-debian.svg" and I put in my .directory file
definition "Icon=system-debian". It doesn't work with this name. 

If I put in the .directory file "Icon=applications-games", it works fine. 

If I make a link from "system-debian.svg" to "applications-games.svg", it
works fine and displays the debian icon so the icon file itself is all right.

I have updated the icon cache.

Is there any limitation on icon names in menu or is it just me (again)?

thanks again
Martin