I get this error while trying to build gtkmm inside JHBuild on Fedora rawhide

make[2]: Entering directory `/home/hendricks/checkout/gnome/gtkmm/gtk/gtkmm'
/bin/sh ../../libtool  --tag=CXX   --mode=compile g++ -DHAVE_CONFIG_H   -I.. -I../.. -I../../gdk  -DG_LOG_DOMAIN=\"gtkmm\" -DGTKMM_BUILD=1 -pthread   -pthread -I/opt/gnome/include/atkmm-1.6 -I/opt/gnome/include/atk-1.0 -I/opt/gnome/include/glibmm-2.4 -I/opt/gnome/lib64/glibmm-2.4/include -I/opt/gnome/include/glib-2.0 -I/opt/gnome/lib64/glib-2.0/include -I/opt/gnome/include/sigc++-2.0 -I/opt/gnome/lib64/sigc++-2.0/include -I/opt/gnome/include/giomm-2.4 -I/opt/gnome/lib64/giomm-2.4/include -I/opt/gnome/include/pangomm-1.4 -I/opt/gnome/lib64/pangomm-1.4/include -I/opt/gnome/include/pango-1.0 -I/opt/gnome/include/gtk-3.0 -I/opt/gnome/include/at-spi2-atk/2.0 -I/opt/gnome/include/gio-unix-2.0/ -I/opt/gnome/include/gdk-pixbuf-2.0 -I/opt/gnome/include/harfbuzz -I/opt/gnome/include/gtk-3.0/unix-print -I/usr/include/cairomm-1.0 -I/usr/lib64/cairomm-1.0/include -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng15 -I/usr/include/libdrm    -Wall -g -O2 -MT entry.lo -MD -MP -MF .deps/entry.Tpo -c -o entry.lo entry.cc
libtool: compile:  g++ -DHAVE_CONFIG_H -I.. -I../.. -I../../gdk -DG_LOG_DOMAIN=\"gtkmm\" -DGTKMM_BUILD=1 -pthread -pthread -I/opt/gnome/include/atkmm-1.6 -I/opt/gnome/include/atk-1.0 -I/opt/gnome/include/glibmm-2.4 -I/opt/gnome/lib64/glibmm-2.4/include -I/opt/gnome/include/glib-2.0 -I/opt/gnome/lib64/glib-2.0/include -I/opt/gnome/include/sigc++-2.0 -I/opt/gnome/lib64/sigc++-2.0/include -I/opt/gnome/include/giomm-2.4 -I/opt/gnome/lib64/giomm-2.4/include -I/opt/gnome/include/pangomm-1.4 -I/opt/gnome/lib64/pangomm-1.4/include -I/opt/gnome/include/pango-1.0 -I/opt/gnome/include/gtk-3.0 -I/opt/gnome/include/at-spi2-atk/2.0 -I/opt/gnome/include/gio-unix-2.0/ -I/opt/gnome/include/gdk-pixbuf-2.0 -I/opt/gnome/include/harfbuzz -I/opt/gnome/include/gtk-3.0/unix-print -I/usr/include/cairomm-1.0 -I/usr/lib64/cairomm-1.0/include -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng15 -I/usr/include/libdrm -Wall -g -O2 -MT entry.lo -MD -MP -MF .deps/entry.Tpo -c entry.cc  -fPIC -DPIC -o .libs/entry.o
entry.cc: In static member function 'static void Gtk::Entry_Class::class_init_function(void*, void*)':
entry.cc:298:25: error: invalid conversion from 'void (*)(GtkEntry*, GtkMenu*) {aka void (*)(_GtkEntry*, _GtkMenu*)}' to 'void (*)(GtkEntry*, GtkWidget*) {aka void (*)(_GtkEntry*, _GtkWidget*)}' [-fpermissive]
   klass->populate_popup = &populate_popup_callback;
                         ^
entry.cc: In static member function 'static void Gtk::Entry_Class::populate_popup_callback(GtkEntry*, GtkMenu*)':
entry.cc:343:37: error: cannot convert 'GtkMenu* {aka _GtkMenu*}' to 'GtkWidget* {aka _GtkWidget*}' in argument passing
     (*base->populate_popup)(self, p0);
                                     ^
entry.cc: In member function 'virtual void Gtk::Entry::on_populate_popup(Gtk::Menu*)':
entry.cc:1461:64: error: cannot convert 'GtkMenu* {aka _GtkMenu*}' to 'GtkWidget* {aka _GtkWidget*}' in argument passing
     (*base->populate_popup)(gobj(),(GtkMenu*)Glib::unwrap(menu));
                                                                ^
make[2]: *** [entry.lo] Error 1
make[2]: Leaving directory `/home/hendricks/checkout/gnome/gtkmm/gtk/gtkmm'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/home/hendricks/checkout/gnome/gtkmm'
make: *** [all] Error 2