Hi all; Not sure whether this is the right place for this message, but a colleague is using breqn, which pulls in a lot of l3kernel stuff, and also mathstyle. Unfortunately, it appears that the package mathstyle redefines \genfrac with a different argument order than amsmath. (and worse, wants to be loaded after amsmath, so you're stuck with the redefinition) mathstyle's api seems to be: \genfrac{style}{open}{close}{thickness}{numer}{denom} while amsmath's is \genfrac{open}{close}{thickness}{style}{numer}{denom} Is there a good reason for this? thanks bruce