Program works in real, not virtual

[Tonig00]

Helo

I have written a short program:

EXPORT ElM1(n,f1,f2)
BEGIN
LOCAL m1;
rowSwap(IDENMAT(n),f1,f2)▶m1;
RETURN m1;
END;

And it works in the real calculator (ROM 2.1.14597) changing the rows of a Identity matrix, but gives me error in the virtual one (ROM 2.1.14592):
"rowSwap(IDENMAT(n),f1,f2) Error: Bad Argument Type"

Do you heve some idea how to solve this small error?

Thanks very much

Toni