diff --git a/ChangeLog b/ChangeLog
index 66025e9246..95aeefcc25 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Aug 19 21:14:22 2008  Tanaka Akira  <akr@fsij.org>
+
+	* include/ruby/io.h (FMODE_READWRITE): define as
+	  FMODE_READABLE|FMODE_WRITABLE.
+
 Tue Aug 19 21:13:08 2008  Tanaka Akira  <akr@fsij.org>
 
 	* io.c (rb_io_flags_mode): use hexadecimal in error message.
diff --git a/include/ruby/io.h b/include/ruby/io.h
index 5d8c7e7141..c6c465b5ed 100644
--- a/include/ruby/io.h
+++ b/include/ruby/io.h
@@ -74,8 +74,7 @@ typedef struct rb_io_t {
 
 #define FMODE_READABLE                  0x0001
 #define FMODE_WRITABLE                  0x0002
-#define FMODE_READWRITE                 0x0003
-
+#define FMODE_READWRITE                 (FMODE_READABLE|FMODE_WRITABLE)
 #define FMODE_BINMODE                   0x0004
 #define FMODE_SYNC                      0x0008
 #define FMODE_TTY                       0x0010