diff --git a/src/api/options.cpp b/src/api/options.cpp
index c77abdceb..b488c36e4 100644
--- a/src/api/options.cpp
+++ b/src/api/options.cpp
@@ -4,6 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 
 Author: Leonardo de Moura
 */
+#include <string>
 #include "util/sstream.h"
 #include "api/name.h"
 #include "api/string.h"