can't export org-tables to LaTeX / void error - org-list-allow-alphabetical

[Benjamin Slade <slade@jnanam.net>]

I have some older org files which once exported to LaTeX without
complaint but now refuse to do so, producing the error
 "defconst: Symbol's value as variable is void:
 org-list-allow-alphabetical"

These files have org-tables in them; if removed, the files export
without any problem.

I haven't set org-list-allow-alphabetical anywhere in my .emacs

I'm running the latest version of org & org-plus-contrib from ELPA.

Suggestions?
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Dr Benjamin Slade <http://www.jnanam.net/slade>
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