diff --git a/include/mapnik/util/conversions.hpp b/include/mapnik/util/conversions.hpp
index 8a4c143c5..bf59b25e4 100644
--- a/include/mapnik/util/conversions.hpp
+++ b/include/mapnik/util/conversions.hpp
@@ -29,6 +29,7 @@
 
 // stl
 #include <iosfwd>
+#include <string>
 
 namespace mapnik { namespace util {