diff --git a/gridappsd-field-bus-lib/gridappsd/field_interface/agents/agents.py b/gridappsd-field-bus-lib/gridappsd/field_interface/agents/agents.py
index 7dcfc8e..b5530d4 100644
--- a/gridappsd-field-bus-lib/gridappsd/field_interface/agents/agents.py
+++ b/gridappsd-field-bus-lib/gridappsd/field_interface/agents/agents.py
@@ -136,10 +136,10 @@ def subscribe_to_measurement(self):
     def subscribe_to_messages(self):
 
         self.downstream_message_bus.subscribe(
-            t.field_message_bus_topic(self.downstream_message_bus),
+            t.field_message_bus_topic(self.downstream_message_bus.id),
             self.on_downstream_message)
         self.upstream_message_bus.subscribe(
-            t.field_message_bus_topic(self.upstream_message_bus),
+            t.field_message_bus_topic(self.upstream_message_bus.id),
             self.on_upstream_message)
 
         _log.debug(
diff --git a/gridappsd-python-lib/gridappsd/topics.py b/gridappsd-python-lib/gridappsd/topics.py
index 87bf567..2934abe 100644
--- a/gridappsd-python-lib/gridappsd/topics.py
+++ b/gridappsd-python-lib/gridappsd/topics.py
@@ -184,8 +184,8 @@ def field_message_bus_topic(message_bus_id:str, app_id: str=None, agent_id: str=
     :return:
     """
     assert message_bus_id, "message_bus_id cannot be empty"
-    
-    return f"{BASE_FIELD_TOPIC}.{message_bus_id}.{app_id}.{agent_id}" 
+
+    return f"{BASE_FIELD_TOPIC}.{message_bus_id}" 
 
 
 def field_message_bus_app_topic(message_bus_id, app_id=None):