Can't change project key for project that has a lead with a changed username

final ErrorCollection validationErrors = validateUpdateProjectData(directoryUser, name, oldProjectResult.getProject(),
                ApplicationUsers.getKeyFor(lead), url, assigneeType, avatarId);

private ErrorCollection validateUpdateProjectData(User user, String name, Project oldProject, String leadName,
            String url, Long assigneeType, Long avatarId)
    {
        final ErrorCollection errorCollection = new SimpleErrorCollection();
        final I18nHelper i18nHelper = getI18nBean(user);

        validateProjectNameForUpdate(name, oldProject.getKey(), errorCollection, i18nHelper);
        validateProjectLead(leadName, errorCollection, i18nHelper);
        validateProjectUrl(url, errorCollection, i18nHelper);
        validateProjectAssigneeType(assigneeType, errorCollection, i18nHelper);
        validateAvatarId(avatarId, oldProject, errorCollection, i18nHelper);

        return errorCollection;
    }