Error in spanishstemmer_search_preprocess() parameter

Today I moved a site to a new server with PHP 5.3.2-1ubuntu4.10.
I get this error message:
Parameter 1 to spanishstemmer_search_preprocess() expected to be a reference, value given in xxxx/includes/module.inc on line 461.

I changed the parameter in the function on line 19 from:
function spanishstemmer_search_preprocess(&$text)
into
function spanishstemmer_search_preprocess($text)
and now it works as expected.