Icons are not showing correctly (X11)

After upgrading xfce4-panel from 4.18 to 4.20, icons are not showing correctly in the tasklist.

The problem is that it always uses the largest icon available and then reduces it to the configured size.

Example:

I fixed it by changing this:

return MAX(wb->width, wb->height) - MAX(wa->width, wb->height);

By:

return MAX(wa->width, wa->height) - MAX(wb->width, wb->height);

In the file: xfw-wnck-icon.c

And now it shows correctly:

NOTE: I'm new, sorry if I did something wrong. And my English is bad, sorry