diff --git a/libc/kernel/uapi/linux/tty.h b/libc/kernel/uapi/linux/tty.h
index 48fa908..dcce572 100644
--- a/libc/kernel/uapi/linux/tty.h
+++ b/libc/kernel/uapi/linux/tty.h
@@ -47,4 +47,5 @@
 #define N_NCI 25
 #define N_SPEAKUP 26
 #define N_NULL 27
+#define N_MCTP 28
 #endif