diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 6810145..c56088e 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -621,7 +621,7 @@
 			} else {
 				split->block_len = split->len;
 				split->block_start = em->block_start + diff;
-				split->orig_start = split->start;
+				split->orig_start = em->orig_start;
 			}
 
 			ret = add_extent_mapping(em_tree, split);