Index: src/Common/utility.h
===================================================================
--- src/Common/utility.h	(revision 447c35601995880f86baa595fb0755c65564b620)
+++ src/Common/utility.h	(revision af98d27936a771ce32ed062a2c90bedf7ddf329e)
@@ -18,4 +18,5 @@
 #include <cctype>
 #include <algorithm>
+#include <functional>
 #include <iostream>
 #include <iterator>