diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index ad8e342c4b7843b0260fa2e92677d703c61e4b9e..5864f05243c21cfa53079f5f2137d528093fc279 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3921,7 +3921,8 @@ static int btrfs_add_system_chunk(struct btrfs_root *root,
 	u8 *ptr;
 
 	array_size = btrfs_super_sys_array_size(super_copy);
-	if (array_size + item_size > BTRFS_SYSTEM_CHUNK_ARRAY_SIZE)
+	if (array_size + item_size + sizeof(disk_key)
+			> BTRFS_SYSTEM_CHUNK_ARRAY_SIZE)
 		return -EFBIG;
 
 	ptr = super_copy->sys_chunk_array + array_size;