diff --git a/include/boost/geometry/multi/algorithms/num_points.hpp b/include/boost/geometry/multi/algorithms/num_points.hpp
index 180523a98..ac10ddff4 100644
--- a/include/boost/geometry/multi/algorithms/num_points.hpp
+++ b/include/boost/geometry/multi/algorithms/num_points.hpp
@@ -15,6 +15,7 @@
 #ifndef BOOST_GEOMETRY_MULTI_ALGORITHMS_NUM_POINTS_HPP
 #define BOOST_GEOMETRY_MULTI_ALGORITHMS_NUM_POINTS_HPP
 
+#include <cstddef>
 
 #include <boost/range.hpp>
 
@@ -34,7 +35,8 @@ namespace detail { namespace num_points
 struct multi_count
 {
     template <typename MultiGeometry>
-    static inline size_t apply(MultiGeometry const& geometry, bool add_for_open)
+    static inline
+    std::size_t apply(MultiGeometry const& geometry, bool add_for_open)
     {
         typedef typename boost::range_value<MultiGeometry>::type geometry_type;
         typedef typename boost::range_iterator