diff --git a/NewKernel_d/include/CGAL/Vector/array.h b/NewKernel_d/include/CGAL/Vector/array.h
index bf03145ebe3..e7ea3e09071 100644
--- a/NewKernel_d/include/CGAL/Vector/array.h
+++ b/NewKernel_d/include/CGAL/Vector/array.h
@@ -31,7 +31,7 @@ template<class NT_,class Dim_,class Max_dim_=Dim_> struct Array_vector {
 	template<class> struct Property : boost::false_type {};
 
 	static const unsigned d_=Max_dim_::value;
-	CGAL_static_assertion(d_ != UNKNOWN_DIMENSION);
+	CGAL_static_assertion(d_ != (unsigned)UNKNOWN_DIMENSION);
 
 	typedef cpp0x::array<NT,d_> Vector;
 	struct Construct_vector {