ICC profiles and Import plugins

I have an import plugin that generates an ICC profile for the image. This works
fine. But in certain rare configurations, I'd like to import the image without a
profile so that it shows up in CS as an untagged image. It seems that I should
only have to set the ICC data pointer to NULL to achieve this, but when I do,
the current working color space is assigned to the image. I suspect that this is
an issue with the color settings in CS, but would like to be sure I'm doing the
right thing in my plugin before chasing that down.