diff --git a/mercurial/sshrepo.py b/mercurial/sshrepo.py
--- a/mercurial/sshrepo.py
+++ b/mercurial/sshrepo.py
@@ -131,6 +131,7 @@ class sshrepository(remoterepository):
         self.call("unlock")
 
     def lookup(self, key):
+        self.requirecap('lookup', _('look up remote revision'))
         d = self.call("lookup", key=key)
         success, data = d[:-1].split(" ", 1)
         if int(success):
@@ -168,6 +169,7 @@ class sshrepository(remoterepository):
         return self.do_cmd("changegroup", roots=n)
 
     def changegroupsubset(self, bases, heads, kind):
+        self.requirecap('changegroupsubset', _('look up remote changes'))
         bases = " ".join(map(hex, bases))
         heads = " ".join(map(hex, heads))
         return self.do_cmd("changegroupsubset", bases=bases, heads=heads)