Polyobject is empty?

I'm getting the error message:

Polyobject 4 is empty
Bad polyobject 4 for anchorpoint

Polyobject is made offmap from a simple 1-sided linedef square containing a 270 trigger tagged 4 referring to a extradata linedef special with PolyObj_StartLine and recordnum 4. Anchorpoint 9300 in offmap; spawnpoint 9301 in-map.

Basically, verbatim copy of the wiki example. And it won't work and it's driving me up the walls. Any help please?

Location: http://www.mediafire.com/download/ybf75800oupcjp4/test.wad

I'll take a look-see this evening. Sounds like you might have found a bug in the polyobj linedef gathering code.

Doubtful. The wiki example level still works correctly.

Bump. And solved: I took the 'args' line in the linedef definition as meaning the 'total number of arguments' instead of the actual argument: the PolyId.