--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -3291,6 +3291,9 @@ def dispatch(args):
continue
for x in external:
+ uisetup = getattr(x, 'uisetup', None)
+ if uisetup:
+ uisetup(u)
cmdtable = getattr(x, 'cmdtable', {})
for t in cmdtable:
if t in table: