Hi, the exception occurs since commit [1]. Not only GtkShortcutsWindow, but also set_help_overlay() function for GtkApplicationWindow have been introduced in GTK+ 3.20 [2].
No requirements bump needed. Please try the patch, I've proposed on [3]. Thanks, Andrey [1] https://git.gnome.org/browse/meld/commit/?id=0039034eb8f67e27464dfb3c1bf05dc54dbc0698 [2] https://git.gnome.org/browse/gtk+/commit/?id=f6d9f9f93de1c3c5a7ab5d9c64783e941189d9b5 [3] https://bugzilla.gnome.org/show_bug.cgi?id=775439
