diff --git a/libc/kernel/uapi/linux/btrfs.h b/libc/kernel/uapi/linux/btrfs.h
index d73527e..506238f 100644
--- a/libc/kernel/uapi/linux/btrfs.h
+++ b/libc/kernel/uapi/linux/btrfs.h
@@ -176,6 +176,7 @@
 #define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE (1ULL << 0)
 #define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID (1ULL << 1)
 #define BTRFS_FEATURE_COMPAT_RO_VERITY (1ULL << 2)
+#define BTRFS_FEATURE_COMPAT_RO_BLOCK_GROUP_TREE (1ULL << 3)
 #define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF (1ULL << 0)
 #define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL (1ULL << 1)
 #define BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS (1ULL << 2)