Kolourpaint max vertical size

On NixOS unstable branch, 32766 pixel is the maximum vertical image size I can save images without corruption in kolourpaint.

I can save 1700x32760 image in png/ppm/xpm formats correctly.
However, 1700x40000 image is corrupted when saved in all the formats above.

I filed a bug report (id=487114) for only PPM format but it looks like this affect all of the formats.

Is this really a bug? or something expected?

32767 = 7FFF = Max 16 Bits integer. Looks like a bug to me.