diff --git a/ChangeLog b/ChangeLog
index b447a68298..2472558606 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Oct 18 11:29:32 2004  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* io.c (rb_io_flags_mode, rb_io_mode_flags): distinguish whether file
+	  not existing is created.  [ruby-dev:24505]
+
 Mon Oct 18 07:26:21 2004  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* file.c (rb_file_truncate): discard read buffer before truncation.
diff --git a/io.c b/io.c
index 1f2a351624..e1acaca1a8 100644
--- a/io.c
+++ b/io.c
@@ -2304,6 +2304,9 @@ rb_io_flags_mode(flags)
       case FMODE_WRITABLE:
 	return MODE_BINMODE("w", "wb");
       case FMODE_READWRITE:
+	if (flags & FMODE_CREATE) {
+	    return MODE_BINMODE("w+", "wb+");
+	}
 	return MODE_BINMODE("r+", "rb+");
     }
     rb_raise(rb_eArgError, "illegal access mode %o", flags);
@@ -2322,10 +2325,10 @@ rb_io_mode_flags(mode)
 	flags |= FMODE_READABLE;
 	break;
       case 'w':
-	flags |= FMODE_WRITABLE;
+	flags |= FMODE_WRITABLE | FMODE_CREATE;
 	break;
       case 'a':
-	flags |= FMODE_WRITABLE | FMODE_APPEND;
+	flags |= FMODE_WRITABLE | FMODE_APPEND | FMODE_CREATE;
 	break;
       default:
       error:
diff --git a/rubyio.h b/rubyio.h
index efafe0c6a8..0b77fa1794 100644
--- a/rubyio.h
+++ b/rubyio.h
@@ -31,6 +31,7 @@ typedef struct OpenFile {
 #define FMODE_WRITABLE  2
 #define FMODE_READWRITE 3
 #define FMODE_APPEND   64
+#define FMODE_CREATE  128
 #define FMODE_BINMODE   4
 #define FMODE_SYNC      8
 #define FMODE_WBUF     16