[O] Exporting a subtree

[Peter Davis]

For the first time, I'm trying to export just a single subtree of my overall 
document, by typing

C-c C-e C-s H O

However, I get this error:

apply: Wrong type argument: listp, #("Details, November 2015" 0 22 (:parent 
(#0)))

The portion in quotes is the overall title of my document.

Should this work? Is there something I need to do differently?

Thank you!

-pd