Valkov, who made his refereeing debut in the domestic top flight five years ago, had been banned for an unspecified period, the BFU's refereeing commission said in a statement on Thursday.
The suspension came following a protest from Lokomotiv, who said referees "were sent to help the hosts", adding Ludogorets scored three of their goals due to poor officiating.
Ludogorets are level on 50 points with Litex Lovech but lie second in the table with a game in hand due to an inferior head-to-head record against the leaders heading into Bulgaria's two-month winter break. Lokomotiv are 10th on 25 points.
Refereeing bans are not uncommon in Bulgaria and several officials have been suspended in recent seasons for below-par performances.
(Reporting by Angel Krasimirov; Editing by John O'Brien)
