diff --git a/include/kabufuda/Util.hpp b/include/kabufuda/Util.hpp
index c50a131..cfa8a5f 100644
--- a/include/kabufuda/Util.hpp
+++ b/include/kabufuda/Util.hpp
@@ -32,6 +32,7 @@
 #include <algorithm>
 #include <string>
 #include <string.h>
+#include "WideStringConvert.hpp"
 
 #undef bswap16
 #undef bswap32