Barcelona overcame the 2-1 draw to beat Levante 4-2 to reach the Copa del Rey quarter-finals.
Two goals from Ousmane Dembele in the first half put the Barça winners in the last four seasons – ahead in the aggregate at the Camp Nou.
Lionel Messi scored a third, his seventh goal in five games.
However, Barca could be expelled from the competition amid allegations that they put an ineligible player in the first match.
Levante said they would file a complaint to the Spanish federation because Barça defender Juan Brandariz should have been suspended after receiving a yellow card while playing for Barcelona's B-team in the second division.
Barcelona said a change in rules, made in November, meant the suspension did not apply to the Copa del Rey.
Real Madrid was kicked out of the cup in 2015 by putting Denis Cheryshev on the field when he was not eligible.
Barcelona were always in control of the second game against Levante, despite facing the prospect of their first exit to the Copa del Rey in nine years.
Messi had a good chance of saving before Barcelona took the lead as Erick Cabaco's strike hit Dembele's right-footer and he threw the ball past Levante goalkeeper Aitor Fernandez.
A minute later, Fernandez inadvertently turned a Dembele chip into his own net while diving to make a save.
On 54 minutes, Dembele crossed to Messi from the right before the Argentinian kicked to the bottom corner.