diff -r 83ce99f5e7f2 -r d900f74456cc mercurial/localrepo.py
--- a/mercurial/localrepo.py	Tue Oct 10 10:03:01 2023 +0200
+++ b/mercurial/localrepo.py	Tue Oct 10 10:03:09 2023 +0200
@@ -1114,7 +1114,7 @@
 
     chainspan = ui.configbytes(b'experimental', b'maxdeltachainspan')
     if 0 <= chainspan:
-        options[b'maxdeltachainspan'] = chainspan
+        delta_config.max_deltachain_span = chainspan
 
     mmapindexthreshold = ui.configbytes(b'experimental', b'mmapindexthreshold')
     if mmapindexthreshold is not None: