1 files changed, 1 insertions, 0 deletions
diff --git a/rubyio.h b/rubyio.h
index fb012045f1..214128449f 100644
--- a/rubyio.h
+++ b/rubyio.h
@@ -31,6 +31,7 @@ typedef struct OpenFile {
 #define FMODE_READWRITE 3
 #define FMODE_BINMODE   4
 #define FMODE_SYNC      8
+#define FMODE_WBUF     16
 
 #define GetOpenFile(obj,fp) rb_io_check_closed((fp) = RFILE(rb_io_taint_check(obj))->fptr)