Bukavshin oversight

15y old Russian player Ivan Bukavshin played a very good tournament in Aeroflot, with a GM norm. But here he forgot something against former FIDE world champion Khalifman (it's good to see him againt in tournaments!).

Khalifman, Alexander(2638) vs. Bukavshin, Ivan(2458)
Aeroflot Open 2011 A - Moscow - 2011.02.16

[Event "Aeroflot Open 2011 A"] [Site "Moscow"] [Date "2011.02.16"] [Round "9"] [White "Khalifman, Alexander"] [Black "Bukavshin, Ivan"] [Result "1-0"] [ECO "A29"] [WhiteElo "2638"] [BlackElo "2458"] [SetUp "1"] [FEN "2k4r/pp3p2/1np3q1/2Q3p1/3R4/1P2P1P1/P4PB1/6K1 w - - 0 24"] [PlyCount "1"] [EventDate "2011.??.??"] 24. Bh3+ 1-0

8 7 6 5 4 3 2 1 abcdefgh

Black just played Qg6. Which tactical problem did he overlook ?