[Therion] Rope line

Hi I was trying to add a line:rope to a map, but without any success. In the data.mp file I see there is a definition of the "l_rope" line, which is equal to the "l_rope_SKBB", but the rope line I drew didn't appear with either the UIS or the SKBB symbol-set. I also tried including some metapost code in the layout to define the line, but again without result. The metapost worked for other line types like ropeladder, but not for rope. A workaround is to define a custom symbol "u:rope", but I wonder why the built-in one doesn't work. Any ideas? Vladimir