diff --git a/src/os/bluestore/BlueStore.cc b/src/os/bluestore/BlueStore.cc
index 1dd1751d4d7..bc83fa1d1a3 100644
--- a/src/os/bluestore/BlueStore.cc
+++ b/src/os/bluestore/BlueStore.cc
@@ -7705,6 +7705,7 @@ int BlueStore::_do_write(
         head_bl.claim_append(bl);
         bl.swap(head_bl);
         offset = gc_start_offset;
+	length = end - offset;
       } else {
         o->extent_map.fault_range(db, gc_start_offset, read_len);
         _do_write_data(txc, c, o, gc_start_offset, read_len, head_bl, &wctx);