minres() does not minimize first module

[steenpass]

Consider the following example:

> ring r = 0, (x,y), dp;
> module m = x*gen(1)+gen(2), y*gen(2);
> resolution s = res(m, 0);
> print(betti(s, 0), "betti");
           0     1
------------------
    0:     1     1
    1:     1     1
------------------
total:     2     2

> print(betti(s, 1), "betti");
           0     1
------------------
    0:     1     -
    1:     -     1
------------------
total:     1     1

> resolution s_min = minres(s);
> print(betti(s_min, 0), "betti");
           0     1
------------------
    0:     1     1
    1:     1     1
------------------
total:     2     2

> 

I would expect the last betti table to be the same as the second to last one.