Equivalence of pseudo-limits

Hi all, Given an indexing 2-category J, a pair of parallel functors F,G : J ----> CAT, and a natural equivalence f : F ==> G, the pseudo-limits of F and G should be equivalent. I am trying to find out what paper, if any, I can cite for this theorem. Or maybe this is just the type of thing that nobody has bothered to write down. Any help would be appreciated. best, Alex Hoffnung