diff --git a/contrib/include/wx/canvas/bbox.h b/contrib/include/wx/canvas/bbox.h
index 6effa6951f..49a2e555ac 100644
--- a/contrib/include/wx/canvas/bbox.h
+++ b/contrib/include/wx/canvas/bbox.h
@@ -21,7 +21,7 @@ class wxBoundingBox
 {
 public:
     wxBoundingBox();
-    wxBoundingBox(wxBoundingBox&);
+    wxBoundingBox(const wxBoundingBox&);
     wxBoundingBox(const wxPoint2DDouble&);
     wxBoundingBox(double xmin, double ymin, double xmax, double ymax);
 
diff --git a/contrib/src/canvas/bbox.cpp b/contrib/src/canvas/bbox.cpp
index 227b0d1c33..b284a86c76 100644
--- a/contrib/src/canvas/bbox.cpp
+++ b/contrib/src/canvas/bbox.cpp
@@ -26,7 +26,7 @@ wxBoundingBox::wxBoundingBox()
 }
 
 
-wxBoundingBox::wxBoundingBox(wxBoundingBox &other)
+wxBoundingBox::wxBoundingBox(const wxBoundingBox &other)
 {
     m_minx = other.m_minx;
     m_miny = other.m_miny;