diff --git a/src/plugins/sib-mention-autocomplete.js b/src/plugins/sib-mention-autocomplete.js
index 5c8ccedcbd0024bcd39c5d5863dac409d780daf2..3e04a552b8af6c4b1bed66cd932d0dc1ea10dedd 100644
--- a/src/plugins/sib-mention-autocomplete.js
+++ b/src/plugins/sib-mention-autocomplete.js
@@ -5,11 +5,13 @@ converse.plugins.add('sib-mention-autocomplete', {
   overrides: {
     ChatRoom: {
       /**
+       * Get all known nicknames from the occupants of the room.
        * Move the `all` mention at the bottom.
+       *
        * @returns {*}
        */
       getAllKnownNicknames() {
-        const nicknames = this.__super__.getAllKnownNicknames.apply(this, arguments);
+        const nicknames = [...new Set(this.occupants.map(o => o.get('nick')).filter(n => n))];
 
         if (nicknames.indexOf('all') >= 0) {
           return nicknames.filter(n => n !== 'all').concat(['all']);