unexpected condition number of matrix



hello group,

i'm calculating the condition numbers of a matrix (wxmaxima 5.11.0):

(%i1) load("linearalgebra");
(%i2) B: matrix([3,4],[4,5]);
(%i3) mat_cond(B,1);    --> 84 
(%i4) mat_cond(B,inf);  --> 84

which should be 24.
I was surprised and calculated the matrix norm (which was also 'wrong') 
and also

(%i5) B^^-1;            --> [ 5 -3]
                            [-4  3]

which I expected to be  1/3* above.

Is there some 'default setting' behind the scene I am missing?
Please, What have I to do to get the right results?

-- 
HTH  Wolfgang