diff --git a/mercurial/httprepo.py b/mercurial/httprepo.py
--- a/mercurial/httprepo.py
+++ b/mercurial/httprepo.py
@@ -276,9 +276,9 @@ class httprepository(remoterepository):
     def get_caps(self):
         if self.caps is None:
             try:
-                self.caps = self.do_read('capabilities').split()
+                self.caps = util.set(self.do_read('capabilities').split())
             except repo.RepoError:
-                self.caps = ()
+                self.caps = util.set()
             self.ui.debug(_('capabilities: %s\n') %
                           (' '.join(self.caps or ['none'])))
         return self.caps
diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -13,7 +13,7 @@ import re, lock, transaction, tempfile, 
 import os, revlog, time, util, extensions, hook
 
 class localrepository(repo.repository):
-    capabilities = ('lookup', 'changegroupsubset')
+    capabilities = util.set(('lookup', 'changegroupsubset'))
     supported = ('revlogv1', 'store')
 
     def __init__(self, parentui, path=None, create=0):
diff --git a/mercurial/sshrepo.py b/mercurial/sshrepo.py
--- a/mercurial/sshrepo.py
+++ b/mercurial/sshrepo.py
@@ -71,11 +71,11 @@ class sshrepository(remoterepository):
         else:
             self.raise_(repo.RepoError(_("no suitable response from remote hg")))
 
-        self.capabilities = ()
+        self.capabilities = util.set()
         lines.reverse()
         for l in lines:
             if l.startswith("capabilities:"):
-                self.capabilities = l[:-1].split(":")[1].split()
+                self.capabilities.update(l[:-1].split(":")[1].split())
                 break
 
     def readerr(self):