diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -54,6 +54,10 @@
 # Make `hg status` emit cwd-relative paths by default.
 status.relative = yes
 
+[extensions]
+# Make `rebase` available.
+rebase =
+
 [diff]
 git = 1
 """