diff --git a/src/strftime.hpp b/src/strftime.hpp
index 97550222ea6..c9630da410b 100644
--- a/src/strftime.hpp
+++ b/src/strftime.hpp
@@ -16,6 +16,7 @@
 #define STRFTIME_HPP_INCLUDED
 
 #include <ctime>
+#include <string>
 
 namespace util {