- if ( ((left && file_of(s) < file_of(ksq)) || (!left && file_of(s) > file_of(ksq)))
- && (relative_rank(Us, ksq) == RANK_1 && rank_of(ksq) == rank_of(s))
- && (!ei.pi->has_open_file_on_side(Us, file_of(ksq), left)))
+ // Penalize rooks which are trapped inside a king. Penalize more if
+ // king has lost right to castle.
+ if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
+ && rank_of(ksq) == rank_of(s)
+ && relative_rank(Us, ksq) == RANK_1
+ && !ei.pi->has_open_file_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))