diff --git a/IPython/zmq/zmqshell.py b/IPython/zmq/zmqshell.py
index f3cd292..d5071c9 100644
--- a/IPython/zmq/zmqshell.py
+++ b/IPython/zmq/zmqshell.py
@@ -91,11 +91,14 @@ class ZMQDisplayPublisher(DisplayPublisher):
         if metadata is None:
             metadata = {}
         self._validate_data(source, data, metadata)
-        msg = self.session.msg(u'display_data', {}, parent=self.parent_header)
-        msg['content']['source'] = source
-        msg['content']['data'] = data
-        msg['content']['metadata'] = metadata
-        self.pub_socket.send_json(msg)
+        content = {}
+        content['source'] = source
+        content['data'] = data
+        content['metadata'] = metadata
+        self.session.send(
+            self.pub_socket, u'display_data', content,
+            parent=self.parent_header
+        )
 
 
 class ZMQInteractiveShell(InteractiveShell):