1 files changed, 13 insertions, 0 deletions

diff --git a/app/graphql/mutations/issues/set_assignees.rb b/app/graphql/mutations/issues/set_assignees.rb
index a4d1c755b53..8413c89b010 100644
--- a/app/graphql/mutations/issues/set_assignees.rb
+++ b/app/graphql/mutations/issues/set_assignees.rb
@@ -7,6 +7,19 @@ module Mutations
 
       include Assignable
 
+      def assign!(issue, users, mode)
+        permitted, forbidden = users.partition { |u| u.can?(:read_issue, issue) }
+
+        super(issue, permitted, mode)
+
+        forbidden.each do |user|
+          issue.errors.add(
+            :assignees,
+            "Cannot assign #{user.to_reference} to #{issue.to_reference}"
+          )
+        end
+      end
+
       def update_service_class
         ::Issues::UpdateService
       end