How do you get sticky posts to work with categories?

How do you get sticky posts to work with categories?

I have tried:

$query-set( 'ignore_sticky_posts', 0 );

but this just results in an out of memory error.

I have tried restricting posts on the blog page by category, but sticky posts are shown regardless of which category they are in.

Why is this basic functionality so hard to achieve? Is the only option to write two separate custom queries?