Vertcat on large sparse matrices causes segmentation-fault

[Hachi]

I have large sparse matrices resulting from heavy calculations and I
want to vertically concatenate them (either using [A;B] or
vertcat(A,B) )
in Matlab / Octave there's no problem, but in Freemat I get a
segmentation-fault

I suppose Freemat converts to full matrices before concatenating them,
because full(A) causes a segmentation-fault, too

is there any command in Freemat for special handling on concatenating
sparse matrices?
or is there a possibility to implement a selfmade method for that job
(with not too much effort) or to increase Freemat's memory
configuration?

(If this information is important: I'm using FreeMat v4.0)