diff --git a/Periodic_3_triangulation_3/include/CGAL/Periodic_3_triangulation_3.h b/Periodic_3_triangulation_3/include/CGAL/Periodic_3_triangulation_3.h
index 50cd85bc963..942576808b4 100644
--- a/Periodic_3_triangulation_3/include/CGAL/Periodic_3_triangulation_3.h
+++ b/Periodic_3_triangulation_3/include/CGAL/Periodic_3_triangulation_3.h
@@ -295,7 +295,7 @@ public:
   virtual ~Periodic_3_triangulation_3() {}
 
   /** @name Assignment */ //@{
-  Periodic_3_triangulation_3& operator=(Periodic_3_triangulation_3& tr)
+  Periodic_3_triangulation_3& operator=(Periodic_3_triangulation_3 tr)
   {
     swap(tr);
     return *this;