Fix the build due to a typo in the previous commit (suggesting that it was never tested anyway).
Fix the build due to a typo in the previous commit (suggesting that it was never tested anyway).

GNOME/gtkmm,GNOME/gtkmm,johne53/MB3Gtkmm,GNOME/gtkmm,johne53/MB3Gtkmm,johne53/MB3Gtkmm,GNOME/gtkmm