Bug in convert: modulate is broken - introduces colour artefacts

Dear developers,

I've just upgraded from Mandriva 2008.1 to 2009.0, and now have a new
version of convert installed,

-modulate now does something horrible to colours around areas of high
contrast, although it used to work just fine.

Here is a sample image:
  http://richardneill.org/tmp/example.png

And here is an invocation to show the bug:
  convert example.png -modulate 25 error.png

Here is what I see as a result:
  http://richardneill.org/tmp/error.png

Version: ImageMagick 6.4.2 2008-09-15 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2008 ImageMagick Studio LL

The application, btw, is a rather complicated script to generate
opening/closing titles for a video, and to provide a fade in from black
at the start. The expected output should be much darker than the input,
but should not have the ugly colour-errors.

Thanks very much for your help,

Richard



P.S. Please consider adding a bugzilla for ImageMagick.