diff -r 20a4543e9a2b -r 8ba0344f9fb1 mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Thu May 10 22:13:13 2018 -0400
+++ b/mercurial/debugcommands.py	Fri May 11 22:07:43 2018 -0400
@@ -837,8 +837,8 @@
         if output:
             dest.close()
 
-@command('debugextensions', cmdutil.formatteropts, [], norepo=True)
-def debugextensions(ui, **opts):
+@command('debugextensions', cmdutil.formatteropts, [], optionalrepo=True)
+def debugextensions(ui, repo, **opts):
     '''show information about active extensions'''
     opts = pycompat.byteskwargs(opts)
     exts = extensions.extensions(ui)