This is fixed by commit ccd65d51403426e176072af492d832677521af9f This commit causes the locale initialization to skip calling setlocal(foo, "") if the environment variable PERL_SKIP_LOCALE_INIT is set. Instead, the setup code calls setlocale(LC_ALL, NULL) (plus other similar calls for the subcategories) in order to find out what the current locale is. The original poster for this ticket has a workaround for it which involves using a modified copy of Perl core code. This patch defines the C preprocessor variable HAS_SKIP_LOCALE_INIT that can be used by XS writers to discover if the current Perl version needs the workaround or not. -- Karl Williamson --- via perlbug: queue: perl5 status: open https://rt.perl.org:443/rt3/Ticket/Display.html?id=38193