--- a/mercurial/upgrade.py	Tue Apr 02 11:03:46 2019 -0700
+++ b/mercurial/upgrade.py	Wed Mar 27 18:26:54 2019 +0100
@@ -332,7 +332,7 @@
 
     @classmethod
     def fromconfig(cls, repo):
-        return repo.ui.config('experimental', 'format.compression')
+        return repo.ui.config('format', 'revlog-compression')
 
 @registerformatvariant
 class compressionlevel(formatvariant):