--- include/tool/tool_interactive.h.orig	2018-07-13 19:53:52 UTC
+++ include/tool/tool_interactive.h
@@ -27,6 +27,7 @@
 #define __TOOL_INTERACTIVE_H
 
 #include <string>
+#include <functional>
 
 #include <tool/tool_event.h>
 #include <tool/tool_base.h>