GTK L&F: JMenu is drawn without borders under Clearlooks theme

JMenu has no border on GTK L&F when Clearlooks theme on GNOME is used - see attached screenshot.

java version "1.6.0_04"
Java(TM) SE Runtime Environment (build 1.6.0_04-b12)
Java HotSpot(TM) Client VM (build 10.0-b19, mixed mode, sharing)

This issue doesn't occur with other Java L&F or GNOME theme.