Question about mfpetersson

Hello,

I am not sure what exactly am I doing wrong, but I am getting unexpected behavior from mfpetersson which seems to violate linearity. Since <Delta, E_{12}>=0 shouldn't the first line below give <Delta, Delta>? Why is it returning 0 instead?

(12:22) gp > mfpetersson(mfsymbol(mfDelta), mfsymbol(mflinear([mfDelta,mfEk(12)],[1,2])))
%43 = 0
(12:25) gp > mfpetersson(mfsymbol(mfDelta), mfsymbol(mflinear([mfDelta,mfEk(12)],[1,0])))
%44 = 1.0353620568043209223478168122251645932 E-6 + 0.E-44*I
(12:25) gp > mfpetersson(mfsymbol(mfDelta), mfsymbol(mflinear([mfDelta,mfEk(12)],[0,1])))
%45 = 0

Thanks,

Ahmad