diff --git a/ChangeLog b/ChangeLog
index 5b4d112b..19261205 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2009-11-13  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
+
+	Rewritten util::uitos()
+	* src/util.h
+
 2009-11-13  Tatsuhiro Tsujikawa  <t-tujikawa@users.sourceforge.net>
 
 	Code cleanup
diff --git a/src/util.h b/src/util.h
index eceb38cb..b60b246e 100644
--- a/src/util.h
+++ b/src/util.h
@@ -47,6 +47,7 @@
 #include <numeric>
 #include <map>
 #include <iomanip>
+#include <algorithm>
 
 #include "SharedHandle.h"
 #include "IntSequence.h"
@@ -102,12 +103,13 @@ std::string uitos(T value, bool comma = false)
   while(value) {
     ++count;
     char digit = value%10+'0';
-    str.insert(str.begin(), digit);
-    value /= 10;
     if(comma && count > 3 && count%3 == 1) {
-      str.insert(str.begin()+1, ',');
+      str += ',';
     }
+    str += digit;
+    value /= 10;
   }
+  std::reverse(str.begin(), str.end());
   return str;
 }