Hearts have asked the Scottish Football Association to explain referee Iain Brines' decision not to award them a goal against Ayr United.
The Edinburgh club claim Brines changed his mind during their Scottish Communities League Cup defeat.
Eggert Jonsson bundled the ball over the line and Hearts say Brines initially indicating a goal.
Brines then spoke to assistant Tom Murphy before changing his mind and booking Jonsson for a hand ball.
The Scottish Premier League club want to know why the officials spoke to United players then changed their decision.
First Division side Ayr equalised minutes later before going on to knock Hearts out of the competition on penalties.