diff --git a/addons/mail/static/src/js/mail_followers.js b/addons/mail/static/src/js/mail_followers.js
index 1e481271eda..1fc93781039 100644
--- a/addons/mail/static/src/js/mail_followers.js
+++ b/addons/mail/static/src/js/mail_followers.js
@@ -218,7 +218,9 @@ openerp_mail_followers = function(session, mail) {
             var subtype_list_ul = this.$('.oe_subtype_list');
             subtype_list_ul.empty();
             var records = data[this.view.datarecord.id || this.view.dataset.ids[0]].message_subtype_data;
-            if (records.length > 1) {
+            var nb_subtype = 0;
+            _(records).each(function (record) {nb_subtype++;});
+            if (nb_subtype > 1) {
                 _(records).each(function (record, record_name) {
                     record.name = record_name;
                     record.followed = record.followed || undefined;