Use Connection.get_heartbeat_interval()

celery/worker/loops.py

@@ -29,7 +29,7 @@ def asynloop(obj, connection, consumer, blueprint, hub, qos,
     readers, writers = hub.readers, hub.writers
     hbtick = connection.heartbeat_check
     errors = connection.connection_errors
-    heartbeat = connection.connection.heartbeat  # negotiated
+    heartbeat = connection.get_heartbeat_interval()  # negotiated
     hub_add, hub_remove = hub.add, hub.remove
 
     on_task_received = obj.create_task_handler()