Weddingbee boards

So I have a lovely strapless dress, just off white color with a sweetheart neckline, and relatively thin.  And the bustier that I ordered online just arrived, and it fits well!  Its comfortable and doesn't bulge through my dress when I sit etc.  

When I put the dress on over the bustier all is well initially... and then the dress slides down a bit with respect to the bustier (which is white) and the upper edge of the bustier peeks over the edge of the dresses neckline.  The color difference between the dress is slight, but it still makes the bustier showing a problem.

So.... what should I do?  Safety pin the dress to the bustier?  That's a simple and inelegant solution, but it might work.  Should I hunt for another bustier that has a slightly lower rise?  Should I modify the existing bustier to make its rise lower?  Should I exchange this bustier for a flesh colored one?  In short, I like the way the dress fits and don't want to modify it, so I need another solution.  Help and suggestions needed!

Thanks for the suggestions ladies!  

I've been hunting around and I think I'm going to try something I found that suggested sewing eyelets/hooks to bustier and dress, sort of like tacking it in, but easily removable!  

If that doesn't work I'll probably see about having the bustier actually tacked into the dress.