diff --git a/Boolean_set_operations_2/include/CGAL/Boolean_set_operations_2/Gps_on_surface_base_2.h b/Boolean_set_operations_2/include/CGAL/Boolean_set_operations_2/Gps_on_surface_base_2.h
index 664ef383702..3547a145626 100644
--- a/Boolean_set_operations_2/include/CGAL/Boolean_set_operations_2/Gps_on_surface_base_2.h
+++ b/Boolean_set_operations_2/include/CGAL/Boolean_set_operations_2/Gps_on_surface_base_2.h
@@ -130,7 +130,7 @@ protected:
   bool m_traits_owner;
 
 
-  Aos_2* m_arr;		// the underlying arrangement
+  Aos_2* m_arr;         // the underlying arrangement
   Vertices* m_vertices; // sorted vertices
 
 public: