IssueService: Update Issue without sending notification mails

I already use the CommentManager to delete comments:

for(Comment comment : comments){
		commentManager.delete(comment, false, user);
}

Documentation of the CommentManager:

dispatchEvent - if true then an event of type EventType.ISSUE_COMMENT_DELETED_ID will be dispatched and any notifications listening for that event will be triggered. If false no event will be dispatched. Together with IssueEvent CommentDeletedEvent

I pass false to not trigger the Event. I also replaced the IssueService with the IssueManager:

issue.setSummary(newSummary)
issue.setDescription(newDesc)

issueManager.updateIssue(user, issue, EventDispatchOption.DO_NOT_DISPATCH, false)

Still not working. When running the script, a few hundred mails will be sended. I wonder if any Atlassian employee can answer this simple question…I created this topic almost 2 weeks ago.