diff --git a/paramiko/hostkeys.py b/paramiko/hostkeys.py
index 3ad0fe5..0a9c10b 100644
--- a/paramiko/hostkeys.py
+++ b/paramiko/hostkeys.py
@@ -82,6 +82,9 @@ class HostKeyEntry:
             return '%s %s %s\n' % (','.join(self.hostnames), self.key.get_name(),
                    self.key.get_base64())
         return None
+    
+    def __repr__(self):
+        return '<HostKeyEntry %r: %r>' % (self.hostnames, self.key)
 
 
 class HostKeys (UserDict.DictMixin):
@@ -178,7 +181,7 @@ class HostKeys (UserDict.DictMixin):
         """
         Find a hostkey entry for a given hostname or IP.  If no entry is found,
         C{None} is returned.  Otherwise a dictionary of keytype to key is
-        returned.
+        returned.  The keytype will be either C{"ssh-rsa"} or C{"ssh-dss"}.
         
         @param hostname: the hostname (or IP) to lookup
         @type hostname: str
@@ -186,13 +189,15 @@ class HostKeys (UserDict.DictMixin):
         @rtype: dict(str, L{PKey})
         """
         ret = {}
+        valid = False
         for e in self._entries:
             for h in e.hostnames:
-                if h.startswith('|1|') and (self.hash_host(hostname, h) == h):
+                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
-                elif h == hostname:
-                    ret[e.key.get_name()] = e.key
-        if len(ret) == 0:
+        if not valid:
             return None
         return ret
     
@@ -231,6 +236,9 @@ class HostKeys (UserDict.DictMixin):
     
     def __setitem__(self, hostname, entry):
         # don't use this please.
+        if len(entry) == 0:
+            self._entries.append(HostKeyEntry([hostname], None))
+            return
         for key_type in entry.keys():
             found = False
             for e in self._entries:
@@ -242,6 +250,7 @@ class HostKeys (UserDict.DictMixin):
                 self._entries.append(HostKeyEntry([hostname], entry[key_type]))
     
     def keys(self):
+        # python 2.4 sets would be nice here.
         ret = []
         for e in self._entries:
             for h in e.hostnames:
diff --git a/tests/test_hostkeys.py b/tests/test_hostkeys.py
index b7d9ae9..e9580dd 100644
--- a/tests/test_hostkeys.py
+++ b/tests/test_hostkeys.py
@@ -104,9 +104,14 @@ class HostKeysTest (unittest.TestCase):
             'ssh-rsa': key,
             'ssh-dss': key_dss
         }
-        self.assertEquals(2, len(hostdict))
+        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]))
         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()