PHP Fatal error: Access level to SarniaSolrService::getFieldNames() must be public (as in class SearchApiSolrService)

using latest sarnia dev.

When submitting the form at admin/config/search/search_api/add_server for Sarnia Solr service class, get a fatal error (at-admin and seven themes tested):
PHP Fatal error: Access level to SarniaSolrService::getFieldNames() must be public (as in class SearchApiSolrService) in .../sites/all/modules/sarnia/service.inc on line 6

changing SarniaSolrService::getFieldNames()

protected function getFieldNames(SearchApiIndex $index, $reset = FALSE) {

to

public function getFieldNames(SearchApiIndex $index, $reset = FALSE) {

and reloading the form will then display the Sarnia Solr service field set when Sarnia Solr service class is selected from the select box - this part of the form does not get displayed when the function is protected. a sarnia service class is then be submitted.