diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 40e5b41e91cc..7b61b7b5122f 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1177,7 +1177,22 @@ int insert_inline_extent_backref(struct btrfs_trans_handle *trans,
 					   num_bytes, parent, root_objectid,
 					   owner, offset, 1);
 	if (ret == 0) {
-		BUG_ON(owner < BTRFS_FIRST_FREE_OBJECTID);
+		/*
+		 * We're adding refs to a tree block we already own, this
+		 * should not happen at all.
+		 */
+		if (owner < BTRFS_FIRST_FREE_OBJECTID) {
+			btrfs_crit(trans->fs_info,
+"adding refs to an existing tree ref, bytenr %llu num_bytes %llu root_objectid %llu",
+				   bytenr, num_bytes, root_objectid);
+			if (IS_ENABLED(CONFIG_BTRFS_DEBUG)) {
+				WARN_ON(1);
+				btrfs_crit(trans->fs_info,
+			"path->slots[0]=%d path->nodes[0]:", path->slots[0]);
+				btrfs_print_leaf(path->nodes[0]);
+			}
+			return -EUCLEAN;
+		}
 		update_inline_extent_backref(path, iref, refs_to_add,
 					     extent_op, NULL);
 	} else if (ret == -ENOENT) {
@@ -1397,6 +1412,9 @@ int btrfs_inc_extent_ref(struct btrfs_trans_handle *trans,
 /*
  * __btrfs_inc_extent_ref - insert backreference for a given extent
  *
+ * The counterpart is in __btrfs_free_extent(), with examples and more details
+ * how it works.
+ *
  * @trans:	    Handle of transaction
  *
  * @node:	    The delayed ref node used to get the bytenr/length for