diff --git a/toml/source_location.hpp b/toml/source_location.hpp
index a386710..fa175b5 100644
--- a/toml/source_location.hpp
+++ b/toml/source_location.hpp
@@ -3,6 +3,7 @@
 #ifndef TOML11_SOURCE_LOCATION_HPP
 #define TOML11_SOURCE_LOCATION_HPP
 #include <cstdint>
+#include <sstream>
 
 #include "region.hpp"