diff --git a/include/mapnik/wkt/wkt_grammar_x3_def.hpp b/include/mapnik/wkt/wkt_grammar_x3_def.hpp
index b4bff5e38..db44a4ce4 100644
--- a/include/mapnik/wkt/wkt_grammar_x3_def.hpp
+++ b/include/mapnik/wkt/wkt_grammar_x3_def.hpp
@@ -26,6 +26,16 @@
 #include <mapnik/wkt/wkt_grammar_x3.hpp>
 #include <mapnik/geometry/fusion_adapted.hpp>
 
+#ifdef __GNUC__
+// instantiate `is_substitute` for reference T and reference Attribute
+// fixes gcc6 compilation issue
+namespace boost { namespace spirit { namespace x3 { namespace traits {
+template <typename T, typename Attribute, typename Enable>
+struct is_substitute<T&, Attribute&, Enable>
+  : is_substitute<T, Attribute, Enable> {};
+}}}}
+#endif
+
 namespace mapnik { namespace grammar {
 
 namespace x3 = boost::spirit::x3;