Not defined error #147

I have inherited some source code from another developer who has used posthtml-expressions and he has built a page that includes the following tag:

They then created a footer file [footer.html] that contains:

All rights reserved. {{jobcode}}

but I am getting the following error:

/Users/a059565/Sites/BMS_Swiss_source/src/index.html: 'jobcode' is not defined.

As I'm new to posthtml-expressions, is there anything obvious going on here?

Thanks