diff --git a/src/format.hpp b/src/format.hpp
index 32a85f8..fe8565b 100644
--- a/src/format.hpp
+++ b/src/format.hpp
@@ -2,6 +2,8 @@
 
 #include "data_types.hpp"
 
+#include <string>
+
 namespace phosphor
 {
 namespace dbus