diff -Naur CRF++-0.54.orig/path.h CRF++-0.54/path.h
--- CRF++-0.54.orig/path.h	2009-04-05 20:42:35.000000000 +0900
+++ CRF++-0.54/path.h	2011-05-31 01:31:43.845198215 +0900
@@ -8,6 +8,7 @@
 #ifndef CRFPP_PATH_H_
 #define CRFPP_PATH_H_
 
+#include <cstddef>
 #include <vector>
 #include "node.h"