They know a thing or two about a derby in Belgrade and Red Star made sure to take full advantage of their trip to Ibrox by indulging in a little trolling.
The Serbian side face Rangers in the last 16 of the Europa League, with the first leg in Glasgow on Thursday night.
The Old Firm rivalry is known throughout the world as one of the fiercest in football but Red Star vs Partizan is one of the few that can come close.
So you can be sure the Serbian supporter who rocked up to Ibrox with a Celtic flag knew exactly what he was doing as he looked to get under the skin of the home fans.
Rangers fans will have the chance to get their own back when they visit Belgrade next week for the second leg.
Red Star's Marakana stadium is known for being one of the most hostile on the continent, with Gers legend Ally McCoist admitting he's never played in such an intimidating atmosphere.
A capacity crowd of 53,000 is expected for the second leg.
