diff --git a/src/allmydata/client.py b/src/allmydata/client.py
index 97e16bbc3..d261a3b1b 100644
--- a/src/allmydata/client.py
+++ b/src/allmydata/client.py
@@ -258,7 +258,7 @@ class Client(node.Node, pollmixin.PollMixin):
         self._key_generator = None
 
     def get_servers(self, service_name):
-        """ Return set of (peerid, versioned-rref) """
+        """ Return frozenset of (peerid, versioned-rref) """
         assert isinstance(service_name, str)
         return self.introducer_client.get_peers(service_name)