This paper revisits the relevance of wanna contraction for the existence of empty categories. An analysis of wanna contraction is proposed under which empty categories have a role in blocking contraction. It is then shown that alternative analyses (subject sharing, local c-command, and morpholexical analyses) are inadequate. It is suggested that empty categories are a last resort, which can only appear in non-subject LDD constructions because these have to be licensed by inside-out functional uncertainty equations, and the empty categories are needed as the c-structure positions to which these equations are annotated.