The above link contains a patch to fix this issue.
(In reply to fiesh from comment #0)
> The above link contains a patch to fix this issue.
> Reproducible: Always
That was my patch but the bug was already fixed upstream with commit http://git.savannah.gnu.org/cgit/src-highlite.git/commit/configure.ac?id=fa34f435776a40b26b18d1efb697d6441a076f51, included in source-highlight-3.1.8 available in tree.
Sorry, I could have sworn I tried emerging 3.1.8 and the same error came -- which clearly isn't the case.