--- a/app/controllers/concerns/issue_templates_common.rb
+++ b/app/controllers/concerns/issue_templates_common.rb
@@ -109,7 +109,7 @@ module IssueTemplatesCommon
 
       if field == 'watcher_user_ids' && project_id.present?
         issue = Issue.new(tracker_id: tracker_id, project_id: project_id)
-        watchers = helpers.users_for_new_issue_watchers(issue)
+        watchers = users_for_new_issue_watchers_with_limit(issue, nil)
         value[:field_format] = 'list'
 
         value[:possible_values] = watchers.map { |user| "#{user.name} :#{user.id}" }
@@ -149,4 +149,21 @@ module IssueTemplatesCommon
     logger&.info "core_fields_map_by_tracker_id failed due to this error: #{e.message}"
     {}
   end
+
+  # https://github.com/redmine/redmine/blob/master/app/helpers/issues_helper.rb
+  # Returns an array of users that are proposed as watchers
+  # on the new issue form
+  def users_for_new_issue_watchers_with_limit(issue, limit = 21)
+    users = issue.watcher_users.select{|u| u.status == User::STATUS_ACTIVE}
+    if limit.present?
+      assignable_watchers = issue.project.principals.assignable_watchers.limit(limit)
+      if assignable_watchers.size < limit
+        users += assignable_watchers.sort
+      end
+    else
+      assignable_watchers = issue.project.principals.assignable_watchers
+      users += assignable_watchers.sort
+    end
+    users.uniq
+  end
 end

--- a/assets/javascripts/issue_templates.js
+++ b/assets/javascripts/issue_templates.js
@@ -423,12 +423,27 @@ ISSUE_TEMPLATE.prototype = {
     document.getElementById('issue_template').dispatchEvent(changeEvent)
   },
   checkSelectedWatchers: function (values) {
-    let targets = document.querySelectorAll('input[name="issue[watcher_user_ids][]"]')
-    for (let i = 0; i < targets.length; i++) {
-      let target = targets[i]
-      if (values.includes(target.value)) {
-        target.checked = true
+    let targets = document.querySelectorAll('input[type="checkbox"][name="issue[watcher_user_ids][]"]')
+    if (targets.length > 0) {
+      for (let i = 0; i < targets.length; i++) {
+        let target = targets[i]
+        if (values.includes(target.value)) {
+          target.checked = true
+        }
+      }
+    } else {
+      // Click "Search for watchers to add" link to open "Add watchers" dialog
+      document.querySelector('span.search_for_watchers a').click()
+      // Check watchers from template setting
+      let searchTargets = document.querySelectorAll('div#users_for_watcher input[name="watcher[user_ids][]"]')
+      for (let i = 0; i < searchTargets.length; i++) {
+        let target = searchTargets[i]
+        if (values.includes(target.value)) {
+          target.checked = true
+        }
       }
+      // Click "Add" button to apply checked watchers and close the dialog
+      document.querySelector('form#new-watcher-form input[type="submit"]').click()
     }
   },