[gtkmm] cannot compile signal_focus_out_event(): what is my problem?

["Andreas B. Thun" <abt gmx de>]

.cpp:

m_entryId.signal_focus_out_event().connect(slot(*this, &ConstraintEdit::entryIdFocusOut));


void ConstraintEdit::entryIdFocusOut(GdkEventFocus* event)
{
}

.h:

Gtk::Entry       m_entryId;
void entryIdFocusOut(GdkEventFocus* event);


I get:

ConstraintEdit.cpp:64: error: no matching function for call to `
   Glib::SignalProxy1<bool, GdkEventFocus*>::connect(SigC::Slot1<void,
   GdkEventFocus*>)'
/usr/include/gtkmm-2.0/glibmm/signalproxy.h:136: error: candidates are:
   SigC::Connection Glib::SignalProxy1<R, P1>::connect(const SigC::Slot1<R,
   P1>&, bool) [with R = bool, P1 = GdkEventFocus*]
make: *** [ConstraintEdit.o] Fehler 1