Gtk SearchEntry не обрабатывает пробел

#include <gtkmm.h>

class Window : public Gtk::Window {
public:
    Window(): Gtk::Window() {
        this->entry.set_placeholder_text("Сюда печатать");
        this->add(entry);
        this->show_all_children();
    }
    bool on_key_press_event(GdkEventKey* event) override {
        if (event->keyval == GDK_KEY_Escape) {
             get_application()->quit();
        }
        return Gtk::Window::on_key_press_event(event);
    }

    Gtk::SearchEntry entry;
};

int main(int argc, char** argv) {
    auto app = Gtk::Application::create(argc, argv, "org.primer.Primer");
    auto window = Window();
    window.show();
    app->run(window);
}