Well, it gets a little tricky, and it helps to keep in mind that giving a film less exposure than it's intended for (using an EI higher than the ISO) sacrifices detail and tonality in shadowed areas. Of course the highlights and mid-tones get less exposure too, but still sufficient for good pictorial quality.
On the other side of the equation, push development has very little effect on those sacrificed shadows, but boosts density in those areas of the neg that already have the highest densities, the highlights. So the danger here is that the highlights will be sacrificed ("blown") by the overdevelopment.
Ideally, the extra development time should be sufficient only to build the highlight density back to where it would have been had the film been exposed at its ISO rating. While you still will lose some shadow detail, and you may be willing to accept that, at least you won't have the highlights blown too! As wisdom advises, "Expose for the shadows, develop for the highlights."
I'd suggest running a test roll in your intended light at the higher EI, and then having your local lab do "push 1" development to see how it comes out. If that zaps the highlights as well as losing the shadows, then next time you could ask for "push 1/2" if they're willing to do that. My nearby pro lab will do custom pushes on request, but any push instructions need to be written in the customer's hand and initialled.
