diff --git a/libc/kernel/uapi/linux/nbd.h b/libc/kernel/uapi/linux/nbd.h
index 749c38a..3b74393 100644
--- a/libc/kernel/uapi/linux/nbd.h
+++ b/libc/kernel/uapi/linux/nbd.h
@@ -45,6 +45,7 @@
 #define NBD_FLAG_CAN_MULTI_CONN (1 << 8)
 #define NBD_CMD_FLAG_FUA (1 << 16)
 #define NBD_CFLAG_DESTROY_ON_DISCONNECT (1 << 0)
+#define NBD_CFLAG_DISCONNECT_ON_CLOSE (1 << 1)
 #define NBD_REQUEST_MAGIC 0x25609513
 #define NBD_REPLY_MAGIC 0x67446698
 struct nbd_request {