diff --git a/ChangeLog b/ChangeLog
index b39d65fe14..3a7a31c794 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Aug 11 11:01:15 2010  Kenta Murata  <mrkn@mrkn.jp>
+
+	* ext/bigdecimal/bigdecimal.c: don't use // comment.
+
 Wed Aug 11 06:18:20 2010  Tanaka Akira  <akr@fsij.org>
 
 	* ext/pathname/pathname.c (path_stat): Pathname#stat translated
diff --git a/ext/bigdecimal/bigdecimal.c b/ext/bigdecimal/bigdecimal.c
index 2992e9fa5c..8b4cacde47 100644
--- a/ext/bigdecimal/bigdecimal.c
+++ b/ext/bigdecimal/bigdecimal.c
@@ -13,7 +13,7 @@
  *
  */
 
-//#define BIGDECIMAL_DEBUG 1
+/* #define BIGDECIMAL_DEBUG 1 */
 #include "bigdecimal.h"
 
 #include <ctype.h>