4 files changed, 10 insertions, 2 deletions
diff --git a/lib/api/helpers.rb b/lib/api/helpers.rb
index 226a7ddd50e..fb100f3f26c 100644
--- a/lib/api/helpers.rb
+++ b/lib/api/helpers.rb
@@ -83,7 +83,9 @@ module API
     end
 
     def find_project_issue(iid)
-      IssuesFinder.new(current_user, project_id: user_project.id).find_by!(iid: iid)
+      issue = IssuesFinder.new(current_user, project_id: user_project.id).find_by!(iid: iid)
+      issue.migrate_assignee
+      issue
     end
 
     def find_project_merge_request(iid)
diff --git a/lib/api/issues.rb b/lib/api/issues.rb
index 78db960ae28..962609ed64b 100644
--- a/lib/api/issues.rb
+++ b/lib/api/issues.rb
@@ -14,6 +14,8 @@ module API
 
         issues = IssuesFinder.new(current_user, args).execute
 
+        issues.each(&:migrate_assignee)
+
         issues.reorder(args[:order_by] => args[:sort])
       end
 
diff --git a/lib/api/v3/helpers.rb b/lib/api/v3/helpers.rb
index 0f234d4cdad..2683e0b4c92 100644
--- a/lib/api/v3/helpers.rb
+++ b/lib/api/v3/helpers.rb
@@ -2,7 +2,9 @@ module API
   module V3
     module Helpers
       def find_project_issue(id)
-        IssuesFinder.new(current_user, project_id: user_project.id).find(id)
+        issue = IssuesFinder.new(current_user, project_id: user_project.id).find(id)
+        issue.migrate_assignee
+        issue
       end
 
       def find_project_merge_request(id)
diff --git a/lib/api/v3/issues.rb b/lib/api/v3/issues.rb
index cb371fdbab8..14e918502d3 100644
--- a/lib/api/v3/issues.rb
+++ b/lib/api/v3/issues.rb
@@ -22,6 +22,8 @@ module API
 
           issues = IssuesFinder.new(current_user, args).execute.inc_notes_with_associations
 
+          issues.each(&:migrate_assignee)
+
           if !match_all_labels && labels.present?
             issues = issues.includes(:labels).where('labels.title' => labels.split(','))
           end