Glasgow - The Scottish Football Association has slammed the "primitive act" which left one of its match officials injured during Livingston's shock 1-0 win over Rangers.
Assistant referee Calum Spence suffered a wound to the back of his head after a missile was thrown from among the Rangers support at Livingston's Tony Macaroni Arena.
Police are investigating the incident, which left Spence requiring medical treatment before he was able to continue in the Scottish Premiership clash on Sunday.
SFA chief executive Ian Maxwell said: "This kind of primitive act - whether something is thrown at players, staff or officials - should be driven out of the game.
"We all have a responsibility to behave in a responsible manner and respect the game we all love.
"At a time when there is so much to be positive about with regards to Scottish football, hopefully this is a wake-up call for some that there are lines of basic decency that should not be crossed.
"I welcome Rangers' decisiveness in moving quickly to try to identify the individual involved."