5. Kd7! (after Kb7?? Black's new queen will be able to stop the White king from the stalemate trick in the main line by 5....e1=Q 6. c6 Qb4+ 7. Kc8 Ke4 with mate in 7. The difference is that here Black runs out of useful checks) 5. .... e1+Q 6. c6 Qd2+ 7. Kc8 with 8. c7 being unavoidable, after which White has the well-known stalemate with queen vs bishop pawn on the 7th rank.