diff --git a/wp-includes/Text/Diff.php b/wp-includes/Text/Diff.php
index b7eae7daba..dc24b67f71 100644
--- a/wp-includes/Text/Diff.php
+++ b/wp-includes/Text/Diff.php
@@ -205,7 +205,7 @@ class Text_Diff {
      * @param string $line  The line to trim.
      * @param integer $key  The index of the line in the array. Not used.
      */
-    function trimNewlines(&$line, $key)
+    static function trimNewlines(&$line, $key)
     {
         $line = str_replace(array("\n", "\r"), '', $line);
     }