diff --git a/gnome-quod/src/boardpanel.h b/gnome-quod/src/boardpanel.h

index 868b2ee..a7a05ec 100644

--- a/gnome-quod/src/boardpanel.h

+++ b/gnome-quod/src/boardpanel.h

@@ -28,8 +28,8 @@

 class BoardPanel : public Gtk::DrawingArea

 {

 public:

-    static const double dx = 1.0;

-    static const double dy = 1.0;

+    static constexpr double dx = 1.0;

+    static constexpr double dy = 1.0;

     static const Glib::ustring NO_BACKGROUND;

     BoardPanel (const Board* board);