--- a/mercurial/context.py	Thu Aug 01 13:40:46 2024 +0200
+++ b/mercurial/context.py	Thu Aug 01 13:42:34 2024 +0200
@@ -541,7 +541,10 @@
 
     @propertycache
     def _manifestdelta(self):
-        return self._manifestctx.readdelta()
+        base, delta = self._manifestctx.read_any_fast_delta()
+        if base is None:
+            self._manifest = delta
+        return delta
 
     @propertycache
     def _parents(self):