Krita writes incorrect PNG files

Binary package hint: krita

Steps to reproduce:

(1) Install krita and pngcheck:

||/ Name Version Description
+++-=================================================-=================================================-==================================================================================================================
ii dcraw 8.80-1 decode raw digital camera images
ii koffice-data 1:1.6.3-6ubuntu3 common shared data for the KDE Office Suite
ii koffice-libs 1:1.6.3-6ubuntu3 common libraries and binaries for the KDE Office Suite
ii krita 1:1.6.3-6ubuntu3 a pixel-based image manipulation program for the KDE Office Suite
ii krita-data 1:1.6.3-6ubuntu3 data files for Krita painting program
ii latex-xft-fonts 0.1-8 Xft-compatible versions of some LaTeX fonts
ii libruby1.8 1.8.7.72-1ubuntu0.1 Libraries necessary to run Ruby 1.8
ii pngcheck 2.0.0-1.1 PNG file format checker
ii ruby 4.2 An interpreter of object-oriented scripting language Ruby
ii ruby1.8 1.8.7.72-1ubuntu0.1 Interpreter of object-oriented scripting language Ruby 1.8

(2) Open Krita.
(3) Select Grayscale -> "White Background, 640x480".
(4) Click "Use this template".
(5) Save unmodified (or modified - but triggering this behaviour doesn't depend on modifying the image) the newly created image to a PNG file. I tried both the "Fast" and "Small" ends of the compression level setting and both produce PNGs ill-formed according to png-check.

(6) Run pngcheck -v on the resulting image (this output is from the 'fast' image, not the one attached to this bug):
File: test.png (2396 bytes)
  chunk IHDR at offset 0x0000c, length 13
    640 x 480 image, 8-bit grayscale, non-interlaced
  chunk sRGB at offset 0x00025, length 1
    rendering intent = absolute colorimetric
  chunk iCCP at offset 0x00032, length 216: not allowed with sRGB

Expected results: a correct PNG file. What happened instead: an apparently (although it's possible pngcheck is wrong, it gives a detailed reason for its diagnosis) incorrect PNG file.