[R-gui] conversion from tessellation in spatstat package to sp classes ???

is there any way to convert from tessellation to sp classes like
SpatialLines or SpatialPolygons?

library(spatstat)
library(maptools)
x <- runifpoint(42)
t <- dirichlet(x)
plot(t)
plot(x, add=TRUE)

sp <- as(t, "SpatialPolygons")
Error in .classEnv(thisClass) :
  unable to find an environment containing class "tess"

any other suggestion?