diff --git a/source/java/org/alfresco/repo/action/executer/MailActionExecuter.java b/source/java/org/alfresco/repo/action/executer/MailActionExecuter.java
index bbf0b5a1ca..6d523b60fd 100644
--- a/source/java/org/alfresco/repo/action/executer/MailActionExecuter.java
+++ b/source/java/org/alfresco/repo/action/executer/MailActionExecuter.java
@@ -885,6 +885,7 @@ public class MailActionExecuter extends ActionExecuterAbstractBase
                     // set subject line
                     String subject = (String)ruleAction.getParameterValue(PARAM_SUBJECT);
                     List<Object> subjectParams = (List<Object>)ruleAction.getParameterValue(PARAM_SUBJECT_PARAMS);
+                    subjectParams = subjectParams == null ? new ArrayList<Object>() : subjectParams;
                     String localizedSubject = getLocalizedSubject(subject, subjectParams.toArray(), locale);
                     if (locale == null)
                     {