diff -r c53bc2e52514 -r ed5e8a9598ce mercurial/localrepo.py
--- a/mercurial/localrepo.py	Wed Feb 04 11:38:30 2015 -0500
+++ b/mercurial/localrepo.py	Fri Jan 23 17:06:03 2015 -0800
@@ -323,6 +323,9 @@
         maxchainlen = self.ui.configint('format', 'maxchainlen')
         if maxchainlen is not None:
             self.svfs.options['maxchainlen'] = maxchainlen
+        manifestcachesize = self.ui.configint('format', 'manifestcachesize')
+        if manifestcachesize is not None:
+            self.svfs.options['manifestcachesize'] = manifestcachesize
 
     def _writerequirements(self):
         reqfile = self.vfs("requires", "w")