From 4158136f18a25c6b7372cb5345ec29911c52e1b1 Mon Sep 17 00:00:00 2001
From: Marius Balteanu <marius.balteanu@zitec.com>
Date: Tue, 5 Oct 2021 19:32:36 +0000
Subject: [PATCH] Merged r21235 from trunk to 4.2-stable (#35463).

git-svn-id: http://svn.redmine.org/redmine/branches/4.2-stable@21236 e93f8b46-1217-0410-a6f0-8f06a7374b81
---
 app/controllers/watchers_controller.rb | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/app/controllers/watchers_controller.rb b/app/controllers/watchers_controller.rb
index 61681b894..79b809516 100644
--- a/app/controllers/watchers_controller.rb
+++ b/app/controllers/watchers_controller.rb
@@ -158,7 +158,9 @@ class WatchersController < ApplicationController
       rescue
         nil
       end
-    return unless klass && klass.respond_to?('watched_by')
+    return unless klass && Class === klass # rubocop:disable Style/CaseEquality
+    return unless klass < ActiveRecord::Base
+    return unless klass < Redmine::Acts::Watchable::InstanceMethods
 
     scope = klass.where(:id => Array.wrap(params[:object_id]))
     if klass.reflect_on_association(:project)
-- 
2.39.5