Celtic were awarded another penalty on Wednesday night against Motherwell.
Former Scottish Premiership midfielder Michael Stewart has claimed on Twitter that Motherwell will be "absolutely raging" after Celtic were given another penalty against Stephen Robinson's side.
Celtic earned a 1-1 draw at Fir Park and kept their unbeaten run intact which now stretches to 66 games, thanks to a Scott Sinclair penalty in the 88th minute after Mikael Lustig had scored an own goal.
Referee Willie Collum decided to give Celtic a spot-kick after Callum McGregor went down under the challenge of Well substitute Andy Rose late on, with both looking to take control of a loose ball.
Former Hearts and Hibernian midfielder Stewart was astonished on Twitter that Mullins had decided to hand Brendan Rodgers' side a penalty kick, claiming Mullins' point to the spot was a "horrific decision".
Have just seen the penalty in the Motherwell v Celtic game....— Michael Stewart (@mstewart_23) November 29, 2017
What a horrific decision! Motherwell will be absolutely raging
This comes after Celtic were awarded another controversial penalty against The Well on Sunday afternoon, as Scott Sinclair seemed to go down softly under the challenge of Cedric Kipre.
It saw 20-year-old Kipre sent off and Celtic double their lead through Moussa Dembele despite being under the cosh at Hampden Park, which eventually saw Rodgers' side hold aloft the Betfred Cup final trophy with a 2-0 win.
With controversy aplenty, Celtic now face Motherwell for a third time on Saturday as they play host to the likes of Louis Moult, Ryan Bowman and Chris Cadden on Parkhead.