diff --git a/mitogen/core.py b/mitogen/core.py
index 47355861..0c1924e4 100644
--- a/mitogen/core.py
+++ b/mitogen/core.py
@@ -1247,8 +1247,8 @@ class ExternalContext(object):
         for msg in self.channel:
             data = msg.unpickle(throw=False)
             LOG.debug('_dispatch_calls(%r)', data)
-            if msg.src_id not in mitogen.parent_ids:
-                LOG.warning('CALL_FUNCTION from non-parent %r', msg.src_id)
+            if msg.auth_id not in mitogen.parent_ids:
+                LOG.warning('CALL_FUNCTION from non-parent %r', msg.auth_id)
 
             modname, klass, func, args, kwargs = data
             try:
diff --git a/mitogen/unix.py b/mitogen/unix.py
index 87abfaac..b36da281 100644
--- a/mitogen/unix.py
+++ b/mitogen/unix.py
@@ -78,6 +78,7 @@ class Listener(mitogen.core.BasicStream):
         context = mitogen.master.Context(self._router, context_id)
         stream = mitogen.core.Stream(self._router, context_id)
         stream.accept(sock.fileno(), sock.fileno())
+        stream.auth_id = mitogen.context_id
         self._router.register(context, stream)
         sock.send(struct.pack('>LL', context_id, mitogen.context_id))
         sock.close()