diff --git a/docs/source/assets_writer.rst b/docs/source/assets_writer.rst
index 5c12ab0..cf5a4da 100644
--- a/docs/source/assets_writer.rst
+++ b/docs/source/assets_writer.rst
@@ -59,8 +59,10 @@ When running as an online node, Cartographer doesn't know when your bag (or sens
 
    # Finish the first trajectory. No further data will be accepted on it.
    rosservice call /finish_trajectory 0
-   rosservice call /write_state ${HOME}/Downloads/b3-2016-04-05-14-14-00.bag.pbstream
 
+   # Ask Cartographer to serialize its current state.
+   # (press tab to quickly expand the parameter syntax)
+   rosservice call /write_state "{filename: '${HOME}/Downloads/b3-2016-04-05-14-14-00.bag.pbstream', include_unfinished_submaps: 'true'}"
 
 Once you've retrieved your ``.pbstream`` file, you can run the assets writer with the `sample pipeline`_ for the 3D backpack: