Elena Rybakina said she did not trust the electronic line-calling system at the Madrid Open following a disputed decision in her three-set win against Zheng Qinwen on Sunday.

The world number two from Kazakhstan remonstrated with the umpire after Zheng was awarded an ace for a serve when the Chinese player was 30-0 up and 4-3 down in the second set.

Rybakina, who went on to win 4-6 6-4 6-3, pointed to the mark and asked umpire Julie Kjendlie to come down to have a look at it on the clay court, but the official said she could not do so.

"The system is wrong, this is not a joke," Australian Open champion Rybakina told the official, who said she had to go with the electronic line-calling system.

"Well, with this thing, I won't trust it at all, because there was no mark even close to what the TV showed."

Last year at the Madrid Open, men's player Alexander Zverev was warned for taking a picture of a contested ball mark during another electric line-calling controversy at the tournament.

The German said there was a "malfunction in the system" after a ball was called in, but which he argued had gone wide.

Zverev took his phone out of his bag and took a picture of the mark before being warned for unsportsmanlike conduct.

"It was, I think, similar to what Zverev had last year because it was in front of her nose. You can't see it. It was pretty frustrating," Rybakina added.

"It's kind of a stolen point. I understand it was her serve and she was serving really well, but it's really frustrating."