Is this endgame (sort-of Q vs K) a draw? I think the following endgame is a draw.

[FEN "7k/5BpP/3K2P1/8/8/8/8/4q3 w - - 0 1"]


My reasoning: I'm playing white. I will only move my king, always. Black's king cannot move. If the queen decide to capture any of my pieces, I will take back, so that won't work. And the queen alone cannot checkmate me, but black cannot bring a piece to help, so it looks like it is a draw.

Is there any flaw in my reasoning, and if yes, what is the flaw? Is this endgame really a draw?
According to the Lomonosov tablebases, it's mate in 40 for black. While the queen can't force mate by herself, she can force a zugzwang. In this case, when the bishop is forced to move to e8. Then, it's a matter of giving checks until the queen forks the king and bishop. 

One of the longest variations given is as follows:

[FEN "7k/5BpP/3K2P1/8/8/8/8/4q3 w - - 0 1"]
[Result "0-1"]

1. Kd7 Qb1 2. Be8 Qb8 3. Bf7 Qb7+ 4. Kd6 Qc8 5. Kd5 Qc7 6. Kd4 Qc6 7. Ke5 Qd7 8. Ke4 Qd6 9. Ke3 Qe5+ 10. Kd3 Qf4 11. Kc3 Qe4 12. Kb3 Qd4 13. Ka3 Qd6+ 14. Kb3 Qc5 15. Kb2 Qe3 16. Kc2 Qa3 17. Kd2 Qf3 18. Kc2 Qe3 19. Kb2 Qd3 20. Ka2 Qc3 21. Kb1 Qd2 22. Bb3 Qb4 23. Ka2 Qa5+ 24. Kb2 Qb6 25. Kc3 Qxg6 26. Bc4 Qd6 27. Bd3 g5 28. Be4 Qc5+ 29. Kd3 g4 30. Bh1 Qa3+ 31. Kd2 Qb2+ 32. Kd3 Qb1+ 33. Ke3 Qxh1 34. Kf4 Qe1 35. Kxg4 Qe3 36. Kh4 Qg1 37. Kh3 Kxh7 38. Kh4 Kg6 39. Kh3 Kf5 40. Kh4 Qg4# 0-1