hmm we did check that the fixltx2e change didn't break float's H if the packages are loaded in the expected order (fixltx2e first). I'm not sure it can really do anything sensible if loaded after other packages have redefined latex internals. Even if it detected the situation there's not much it could do other than not make the definition. In general I'd say it can't detect arbitrary packages making arbitrary changes although in this case, perhaps it could make an exception as the main error case it is detecting is using [H] without loading float (which previously took the float to the end of document with no warning) although probably a better fix would be for float to delay its definition to begin document David