diff --git a/ipywidgets/widgets/widget.py b/ipywidgets/widgets/widget.py
index 1f8515aa5e..ff8babb5cd 100644
--- a/ipywidgets/widgets/widget.py
+++ b/ipywidgets/widgets/widget.py
@@ -141,9 +141,9 @@ def handle_comm_opened(comm, msg):
     # Traits
     #-------------------------------------------------------------------------
     _model_module = Unicode(None, allow_none=True, help="""A requirejs module name
-        in which to find _model_name. If empty, look in the global registry.""")
+        in which to find _model_name. If empty, look in the global registry.""", sync=True)
     _model_name = Unicode('WidgetModel', help="""Name of the backbone model
-        registered in the front-end to create and sync this widget with.""")
+        registered in the front-end to create and sync this widget with.""", sync=True)
     _view_module = Unicode(help="""A requirejs module in which to find _view_name.
         If empty, look in the global registry.""", sync=True)
     _view_name = Unicode(None, allow_none=True, help="""Default view registered in the front-end