diff --git a/app/assets/javascripts/discourse/app/models/group.js b/app/assets/javascripts/discourse/app/models/group.js
index 6ce97c898c9..b65f29e61bb 100644
--- a/app/assets/javascripts/discourse/app/models/group.js
+++ b/app/assets/javascripts/discourse/app/models/group.js
@@ -131,7 +131,7 @@ const Group = RestModel.extend({
     return ajax(`/groups/${this.id}/join.json`, {
       type: "PUT",
     }).then(() => {
-      this.findMembers();
+      this.findMembers({}, true);
     });
   },
 
diff --git a/app/controllers/groups_controller.rb b/app/controllers/groups_controller.rb
index 4db8e7b9210..fd09ecba2e5 100644
--- a/app/controllers/groups_controller.rb
+++ b/app/controllers/groups_controller.rb
@@ -398,6 +398,7 @@ class GroupsController < ApplicationController
     end
 
     group = Group.find(params[:id])
+    raise Discourse::NotFound unless group
     raise Discourse::InvalidAccess unless group.public_admission
 
     return if group.users.exists?(id: current_user.id)