Harry Maguire says Manchester United have spoken about the UEFA racial abuse protocol ahead of Thursday's clash with Partizan Belgrade.
The Serbian giants played their last two European home games behind closed doors after racist abuse by supporters.
"We will trust Uefa to follow their protocol," Maguire said.
"Sofia was a sickening atmosphere, something I don't want to be part of again.
"We're positive tomorrow night will be a great atmosphere, one we're all looking forward to playing in.
"If something does goes off, then we'll follow the three-step protocol and I'm sure there will be people on and off the pitch doing their bit to make things better for the future."
