diff --git a/libraries/advisor.class.php b/libraries/advisor.class.php
index 75c8a8d9b8..d6ea9035b3 100644
--- a/libraries/advisor.class.php
+++ b/libraries/advisor.class.php
@@ -81,6 +81,14 @@ class Advisor
         return true;
     }
 
+    /**
+     * Escapes percent string to be used in format string.
+     */
+    function escapePercent($str)
+    {
+        return preg_replace('/%( |,|\.|$)/','%%\1', $str);
+    }
+
     /**
      * Splits justification to text and formula.
      */
@@ -88,7 +96,7 @@ class Advisor
     {
         $jst = preg_split('/\s*\|\s*/', $rule['justification'], 2);
         if (count($jst) > 1) {
-            $jst[0] = preg_replace('/%( |,|\.|$)/','%%\1',$jst[0]);
+            $jst[0] = Advisor::escapePercent($jst[0]);
             return array($jst[0], $jst[1]);
        }
         return array($rule['justification']);