diff --git a/db/migrate/20171106135924_issues_milestone_id_foreign_key.rb b/db/migrate/20171106135924_issues_milestone_id_foreign_key.rb
index e6a780d0964..bfb3dcae511 100644
--- a/db/migrate/20171106135924_issues_milestone_id_foreign_key.rb
+++ b/db/migrate/20171106135924_issues_milestone_id_foreign_key.rb
@@ -16,6 +16,7 @@ class IssuesMilestoneIdForeignKey < ActiveRecord::Migration
 
     def self.with_orphaned_milestones
       where('NOT EXISTS (SELECT true FROM milestones WHERE milestones.id = issues.milestone_id)')
+        .where('milestone_id IS NOT NULL')
     end
   end