Index: src/Common/utility.h
===================================================================
--- src/Common/utility.h	(revision 447c35601995880f86baa595fb0755c65564b620)
+++ src/Common/utility.h	(revision af0c8dabd4bc59ed96120c8fd8004bceb1e3cbbc)
@@ -18,4 +18,5 @@
 #include <cctype>
 #include <algorithm>
+#include <functional>
 #include <iostream>
 #include <iterator>