[R] How to draw holes generated by gpclib using plot function

[Hisaji ONO]

Hi.

 I've tried to create a polygon with one hole by gpclib using following
example script.

 holepoly <- read.polyfile(system.file("poly-ex/hole-poly.txt", package
="gpclib"), nohole = FALSE)
 area.poly(holepoly)
 plot(holepoly,poly.args=list(col="red",border="blue"))

 And I noticed plot function couldn't draw polygons with holes correctly.

 Does anyone know how to solve this situation?

 Regards.