diff --git a/include/linux/tty.h b/include/linux/tty.h
index c7ea9bc..021bfd2 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -367,6 +367,7 @@
 #define TTY_HUPPED 		18	/* Post driver->hangup() */
 #define TTY_FLUSHING		19	/* Flushing to ldisc in progress */
 #define TTY_FLUSHPENDING	20	/* Queued buffer flush pending */
+#define TTY_HUPPING 		21	/* ->hangup() in progress */
 
 #define TTY_WRITE_FLUSH(tty) tty_write_flush((tty))