make 2 FAST=YES

When I say "make 2 FAST=YES" in compiler/, the make system is supposed to recompile the stage-2 compiler, but ignoring the fact that the stage-1 compiler has changed. It used to do that. But now it doesn't. It recompiles every module in GHC, and every module in the base libraries on which GHC depends. The recompilation checker then spots that nothing has changed, but it still takes several unnecessary minutes. Would it be possible to restore the old behaviour? It saves quite a lot of time when rebuilding stage2 after a minor change. Thanks! Simon