diff --git a/IPython/parallel/controller/hub.py b/IPython/parallel/controller/hub.py
index 0516a60..6f9dc89 100644
--- a/IPython/parallel/controller/hub.py
+++ b/IPython/parallel/controller/hub.py
@@ -923,7 +923,7 @@ class Hub(SessionFactory):
                 content=content,
                 ident=reg)
 
-        heart = util.asbytes(uuid)
+        heart = cast_bytes(uuid)
 
         if content['status'] == 'ok':
             if heart in self.heartmonitor.hearts:
diff --git a/IPython/parallel/controller/scheduler.py b/IPython/parallel/controller/scheduler.py
index 34b05ec..a5a4ffe 100644
--- a/IPython/parallel/controller/scheduler.py
+++ b/IPython/parallel/controller/scheduler.py
@@ -261,7 +261,7 @@ class TaskScheduler(SessionFactory):
         
         content = msg['content']
         for uuid in content.get('engines', {}).values():
-            self._register_engine(asbytes(uuid))
+            self._register_engine(cast_bytes(uuid))
 
     
     @util.log_errors