diff -r b79c73a7afce -r 26dcdbe15024 mercurial/revlogutils/deltas.py
--- a/mercurial/revlogutils/deltas.py	Tue Oct 10 11:36:55 2023 +0200
+++ b/mercurial/revlogutils/deltas.py	Tue Oct 10 12:03:02 2023 +0200
@@ -1177,7 +1177,7 @@
                 and self.revlog.length(currentbase) == 0
             ):
                 currentbase = self.revlog.deltaparent(currentbase)
-            if self.revlog._lazydelta and currentbase == base:
+            if self.revlog.delta_config.lazy_delta and currentbase == base:
                 delta = revinfo.cachedelta[1]
         if delta is None:
             delta = self._builddeltadiff(base, revinfo)