The Argentine defender's kneed effort from a corner crossed the line in the 65th minute of City's come-from-behind win at Borussia Park on Wednesday night.
The ball was cleared by Lars Stindl but fell to Nicolas Otamendi who fired home with help from a wicked deflection off Andreas Christensen.
There was conjecture as to who the goal should be awarded to, whether it be Otamendi or an own-goal from Christensen, but sanity has ruled with Demichelis now having his initial attempt recorded.
On the night, the additional assistant referee (AAR) reportedly adjudged that the effort from Demichelis had crossed the line, which has now been acknowledge by UEFA.
A UEFA statement said: "The referee immediately reported that the goal should have been awarded to Martin Demichelis for his initial attempt on goal - and that the additional assistant referee had clearly indicated the ball had crossed the line after that shot.
"As it was too late to correct the identity of the scorer at that time, the audio recordings were reviewed this morning and confirmed the statement of the referee regarding the attribution of the goal to Demichelis. UEFA hereby confirms that decision."
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