Honda will take its second engine upgrade of the 2019 season to Paul Ricard next weekend.
Dr Helmut Marko had said at the time that the Baku upgrade was originally planned for the sixth race in Monaco.
"There are things in the pipeline that should help us in the near future to find that bit we are missing compared to the cars ahead of us," team boss Christian Horner added.
Now, the Dutch newspaper De Telegraaf reveals that the second upgrade will be brought to the French GP.
Honda's development pace is promising, but it does mean that Max Verstappen and the other Honda-powered drivers will already be on their third engines for 2019.
Further upgrades, or engine changes due to failures, will be penalised.
"I believe in our project with Honda," said Verstappen. "We are working hard to improve performance. We will see where we stand in the coming races.
"With more power and a better balance in the car, the situation can look very different."