Pasting selection into snippets does not work on Xorg

Pasting from the selection clipboard (PRIMARY, not CLIPBOARD, details here) does not work. Middle clicking on the text-area does nothing.

This is probably due to the fact that it's not a real text-field, but rather something that's designed to look like one.

Xorg 1.17.2, Firefox 38.0.6.

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As a workaround (and a rather ugly one), I open leafpad, paste into it, select all, ctrl+c, and then ctrl+v into the snippet view.