x-gtk-use-old-file-dialog

x-gtk-use-old-file-dialog is a variable defined in `C source code'.
Its value is

nil

Documentation:
Non-nil means prompt with the old GTK file selection dialog.
If nil or if the file selection dialog is not available, the new GTK file
chooser is used instead. To turn off all file dialogs set the
variable `use-file-dialog'.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.