diff --git a/lib/mathslib.php b/lib/mathslib.php
index 82bf05369be..1640f14385b 100644
--- a/lib/mathslib.php
+++ b/lib/mathslib.php
@@ -115,7 +115,7 @@ class calc_formula {
      * @param string $formula
      * @return string localised formula
      */
-    function localize($formula) {
+    public static function localize($formula) {
         $formula = str_replace('.', '$', $formula); // temp placeholder
         $formula = str_replace(',', get_string('listsep', 'langconfig'), $formula);
         $formula = str_replace('$', get_string('decsep', 'langconfig'), $formula);
@@ -127,7 +127,7 @@ class calc_formula {
      * @param string $formula localised formula
      * @return string
      */
-    function unlocalize($formula) {
+    public static function unlocalize($formula) {
         $formula = str_replace(get_string('decsep', 'langconfig'), '$', $formula);
         $formula = str_replace(get_string('listsep', 'langconfig'), ',', $formula);
         $formula = str_replace('$', '.', $formula); // temp placeholder