Index: src/Common/utility.h
===================================================================
--- src/Common/utility.h	(revision 447c35601995880f86baa595fb0755c65564b620)
+++ src/Common/utility.h	(revision 15e4e229e30d072027f3e0cd4a71759959451647)
@@ -18,4 +18,5 @@
 #include <cctype>
 #include <algorithm>
+#include <functional>
 #include <iostream>
 #include <iterator>