diff --git a/app/assets/javascripts/discourse/components/group-membership-button.js.es6 b/app/assets/javascripts/discourse/components/group-membership-button.js.es6
index a3de6d7ab02..83ad277df27 100644
--- a/app/assets/javascripts/discourse/components/group-membership-button.js.es6
+++ b/app/assets/javascripts/discourse/components/group-membership-button.js.es6
@@ -15,7 +15,7 @@ export default Ember.Component.extend({
 
   @computed("model.is_group_user", "model.id", "groupUserIds")
   userIsGroupUser(isGroupUser, groupId, groupUserIds) {
-    if (isGroupUser) {
+    if (isGroupUser !== undefined) {
       return isGroupUser;
     } else {
       return !!groupUserIds && groupUserIds.includes(groupId);
diff --git a/test/javascripts/components/group-membership-button-test.js.es6 b/test/javascripts/components/group-membership-button-test.js.es6
index b1796078d87..90831ec9c51 100644
--- a/test/javascripts/components/group-membership-button-test.js.es6
+++ b/test/javascripts/components/group-membership-button-test.js.es6
@@ -58,4 +58,11 @@ test('userIsGroupUser', function() {
   this.subject().set('groupUserIds', undefined);
 
   equal(this.subject().get('userIsGroupUser'), false);
+
+  this.subject().setProperties({
+    groupUserIds: [1, 3],
+    model: { id: 1, is_group_user: false }
+  });
+
+  equal(this.subject().get('userIsGroupUser'), false);
 });