diff --git a/3party/boost/boost/polygon/point_data.hpp b/3party/boost/boost/polygon/point_data.hpp
index 23c23ed2b0..e42a7aa78d 100644
--- a/3party/boost/boost/polygon/point_data.hpp
+++ b/3party/boost/boost/polygon/point_data.hpp
@@ -46,6 +46,9 @@ class point_data {
   }
 
   template <typename PointType>
+#ifdef __GNUC__
+  explicit
+#endif
   point_data(const PointType& that) {
     *this = that;
   }