How to force casperjs to save file in utf-8?

Question

Parsing

Good afternoon! Here is a piece of code that saves the page to a file

casper.thenOpen(myurli, function(){

       var page1 = this.getHTML();
       fs.write(file_path, page1, 'wb');
  
});

The file is saved in ANSI, but I need it in utf-8. Please tell me how to do it?