diff --git a/block.c b/block.c
index c1d1f74b88..a027823ea4 100644
--- a/block.c
+++ b/block.c
@@ -3134,6 +3134,8 @@ static int coroutine_fn bdrv_aligned_pwritev(BlockDriverState *bs,
 
     waited = wait_serialising_requests(req);
     assert(!waited || !req->serialising);
+    assert(req->overlap_offset <= offset);
+    assert(offset + bytes <= req->overlap_offset + req->overlap_bytes);
 
     ret = notifier_with_return_list_notify(&bs->before_write_notifiers, req);