diff --git a/include/stdex/sgml.hpp b/include/stdex/sgml.hpp
index b5a533733..e160d78a0 100644
--- a/include/stdex/sgml.hpp
+++ b/include/stdex/sgml.hpp
@@ -10,6 +10,7 @@
 #include "sgml_unicode.hpp"
 #include "string.hpp"
 #include <assert.h>
+#include <string>
 
 namespace stdex
 {