Rare sounds of praise for Renault are emerging from the Red Bull camp ahead of the 2016 season.
Last year, the strained relationship between the two parties broke down completely, meaning that Red Bull lost its title sponsor Infiniti and had to re-brand its customer supply of turbo V6 power as 'Tag Heuer' for the new season.
However, Dr Helmut Marko, formerly the chief critic of Renault's slow progress in the 'power unit' era, is now sounding much more positive.
"The car is fantastic as expected," he told Germany's Auto Bild, "but I am especially satisfied by the work Renault has done over the winter.
"In terms of reliability and responsiveness of the Tag-Heuer Renault, they have done a step."
Some analysts, however, question whether Renault has actually upped its game in pure horse power, but Marko said that the marque's improvements are in fact "finally reflected in laptime".
"If Helmut is praising Renault, then the step on the engine side must be huge," said former Formula 1 driver and long-time Red Bull supporter Gerhard Berger.
Furthermore, Marko said that Renault is planning to take another big step forward after the first handful of races in 2016.
"There is a major performance update planned. Then, podiums on our own steam will even be possible," said Marko.
The new season gets underway with the Australian Grand Prix later this month.
