diff --git a/libc/kernel/uapi/linux/btrfs.h b/libc/kernel/uapi/linux/btrfs.h
index 5220647..9a7a6fa 100644
--- a/libc/kernel/uapi/linux/btrfs.h
+++ b/libc/kernel/uapi/linux/btrfs.h
@@ -107,6 +107,7 @@
   __u64 unverified_errors;
 };
 #define BTRFS_SCRUB_READONLY 1
+#define BTRFS_SCRUB_SUPPORTED_FLAGS (BTRFS_SCRUB_READONLY)
 struct btrfs_ioctl_scrub_args {
   __u64 devid;
   __u64 start;