webContents.print header missing

In my Electron ‘main’ js file, I define the following menu item:

{ label: ‘&Print Current Display’,
click(item, focusedWindow) {
headerStr = 'CSVEdit Display: version: ’ + app.getVersion()
+ ', printed at: ’ + new Date() ;
focusedWindow.webContents.print({
silent: true,
header: headerStr,
printBackground: false
},
(success, errorType) => {
if (success) {
return ;
}
if (!success) {
console.log(errorType) ;
}
})

            } // click
         }, 

However, while the page does print, the ‘header’ does not.
Help!