R Shiny DT datatable change buttons export encoding

I have a shiny application with data displayed with DT. I can export this data with the buttons extensions. But when I export the data, the accent characters do not show correctly.

How can I change the export encoding to have the accents correctly written ?

The original data is

Nom,"Prenom"
Dupond,"Étienne"
Dupont,"François"
Martin,"Frédéric"

This is what I get when I use the CSV or Excel button :

Nom,"Prenom"
Dupond,"Étienne"
Dupont,"François"
Martin,"Frédéric"

Here is a code sample

library(shiny)
library(DT)

ui <- fluidPage(
  DT::DTOutput("table_utilisateurs")
)
server <- function(input, output, session) {
  
  output$table_utilisateurs <- DT::renderDT(server = FALSE, {

    DT::datatable(
      data.frame(Nom = c('Dupond', 'Dupont', 'Martin'),
                 Prenom = c('Étienne', 'François', 'Frédéric')),
      extensions = "Buttons",
      filter = 'top',
      rownames = FALSE,
      options = list(
        pageLength = 10,
        lengthMenu = c(10,20,50,100),
        order = list(list(0,'asc')),
        autoWidth = TRUE,
        dom = 'lftipB',
        buttons = c('copy', 'csv', 'excel')
      )
    )
  })
}
shinyApp(ui, server)