diff --git a/yazio/sites/all/modules/de_stemmer/de_stemmer.module b/yazio/sites/all/modules/de_stemmer/de_stemmer.module
index 71abc47..b773ba6 100644
--- a/yazio/sites/all/modules/de_stemmer/de_stemmer.module
+++ b/yazio/sites/all/modules/de_stemmer/de_stemmer.module
@@ -100,7 +100,7 @@ function _de_stemmer_region_n($wort) {
   return $r + strspn($wort, DE_STEMMER_VOKALE, $r) + 1;
 }
 
-function de_stemmer_preprocess($wort) {
+function _de_stemmer_preprocess($wort) {
   $wort = drupal_strtolower($wort);
   $wort = str_replace("ß", "ss", $wort);
   // replace ß by ss, and put u and y between vowels into upper case
@@ -133,7 +133,7 @@ function _de_stemmer_postprocess($wort) {
 
 
 function _de_stemmer_wortstamm($wort) {
-  $stamm = de_stemmer_preprocess($wort);
+  $stamm = _de_stemmer_preprocess($wort);
 
   /*
     * R1 is the region after the first non-vowel following a vowel,