diff --git a/include/linux/tty.h b/include/linux/tty.h
index 7e605e4..931078b 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -48,6 +48,7 @@
 #define N_PPS		18	/* Pulse per Second */
 #define N_V253		19	/* Codec control over voice modem */
 #define N_CAIF		20      /* CAIF protocol for talking to modems */
+#define N_GSM0710	21	/* GSM 0710 Mux */
 
 /*
  * This character is the same as _POSIX_VDISABLE: it cannot be used as