Firefox: while drag-n-drop tabs, the new location indication arrow gets hidden by the dragged tab

Below is the extract for launchpad bug description: https://bugs.launchpad.net/hundredpapercuts/+bug/853867

As a normal geek, after 1 minute of using a browser, firefox, I have tens of tabs. It happens that I need to rearrange these tabs, so I can move among them faster and to keep some sanity.

The problem is:
while drag-n-drop'ing a tab, I got a small nice arrow that should be indicating where that tab will be seated, that arrow, in fact, appears beneath the Tabs row, so the arrow gets hidden by the captured tab and I can't see if that arrow really exists or not and where it is, which makes me try to move the tab(while still captured) around the line between the two future-neighbour-tabs to see if that arrow does exist. Firefox sometimes, doesn't recognize that I'm actually moving a tab or it just gets stuck, that's why I need to see the arrow.

Please make that arrow appear above the Tabs row while drag-n-drop'ing Tabs. Thanks.