Gueye joined the Goodison Park outfit from Aston Villa in August 2016 and has been a mainstay in the Toffees' midfield.
Koeman disclosed the club are in talks with the 28-year-old to reward his impressive showings with a new deal.
“It’s true that we are in talks with him [Gueye] about a new contract,” Koeman told SkySports.
“I’m really happy with him. I think he had a big impact in that aggression on the midfield last season.
“We lost a little bit of his aggression at the beginning of the season, Morgan [Schneiderlin] was struggling a little bit at the beginning of the season but both players did well against Man United and in that game Gana was perfect, Morgan was good and also last weekend.
“That’s what the team needs because these two players and also Gana is really important if they make that aggression and are winning second balls it is much better for the team," he concluded.