diff --git a/paramiko/hostkeys.py b/paramiko/hostkeys.py
index 0a9c10b..316acc6 100644
--- a/paramiko/hostkeys.py
+++ b/paramiko/hostkeys.py
@@ -188,18 +188,43 @@ class HostKeys (UserDict.DictMixin):
         @return: keys associated with this host (or C{None})
         @rtype: dict(str, L{PKey})
         """
-        ret = {}
-        valid = False
+        class SubDict (UserDict.DictMixin):
+            def __init__(self, hostname, entries, hostkeys):
+                self._hostname = hostname
+                self._entries = entries
+                self._hostkeys = hostkeys
+            
+            def __getitem__(self, key):
+                for e in self._entries:
+                    if e.key.get_name() == key:
+                        return e.key
+                raise KeyError(key)
+            
+            def __setitem__(self, key, val):
+                for e in self._entries:
+                    if e.key is None:
+                        continue
+                    if e.key.get_name() == key:
+                        # replace
+                        e.key = val
+                        break
+                else:
+                    # add a new one
+                    e = HostKeyEntry([hostname], val)
+                    self._entries.append(e)
+                    self._hostkeys._entries.append(e)
+            
+            def keys(self):
+                return [e.key.get_name() for e in self._entries if e.key is not None]
+
+        entries = []
         for e in self._entries:
             for h in e.hostnames:
                 if (h.startswith('|1|') and (self.hash_host(hostname, h) == h)) or (h == hostname):
-                    valid = True
-                    if e.key is None:
-                        continue
-                    ret[e.key.get_name()] = e.key
-        if not valid:
+                    entries.append(e)
+        if len(entries) == 0:
             return None
-        return ret
+        return SubDict(hostname, entries, self)
     
     def check(self, hostname, key):
         """
diff --git a/tests/test_hostkeys.py b/tests/test_hostkeys.py
index e9580dd..2430357 100644
--- a/tests/test_hostkeys.py
+++ b/tests/test_hostkeys.py
@@ -105,13 +105,12 @@ class HostKeysTest (unittest.TestCase):
             'ssh-dss': key_dss
         }
         hostdict['fake.example.com'] = {}
-        # this line will have no effect, but at least shouldn't crash:
         hostdict['fake.example.com']['ssh-rsa'] = key
         
         self.assertEquals(3, len(hostdict))
         self.assertEquals(2, len(hostdict.values()[0]))
         self.assertEquals(1, len(hostdict.values()[1]))
-        self.assertEquals(0, len(hostdict.values()[2]))
+        self.assertEquals(1, len(hostdict.values()[2]))
         fp = hexlify(hostdict['secure.example.com']['ssh-rsa'].get_fingerprint()).upper()
         self.assertEquals('7EC91BB336CB6D810B124B1353C32396', fp)
         fp = hexlify(hostdict['secure.example.com']['ssh-dss'].get_fingerprint()).upper()