Fatal error: Call to undefined function i18n_langcode() ... on line 94

There's a fatal error when using this module that takes down the entire site.

When I assign this to a block region, I get this error:

Fatal error: Call to undefined function i18n_langcode() in /home/okulicom/public_html/dir/sites/all/modules/taxonomy_block/taxonomy_block.module on line 94

Is there a work-around? Can this issue be "fast tracked" so a solution is provided ASAP?

Thanks!