diff --git a/CHANGELOG b/CHANGELOG
index 7215a919d79a9b6390b29d095e91dbb831e274c4..bcb7e290ede4b9fb07b68945830b0cff73a4cebc 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -34,6 +34,7 @@ v 8.9.0 (unreleased)
   - Cache project build count in sidebar nav
   - Reduce number of queries needed to render issue labels in the sidebar
   - Improve error handling importing projects
+  - Remove duplicated notification settings
   - Put project Files and Commits tabs under Code tab
 
 v 8.8.4
diff --git a/db/migrate/20160603180330_remove_duplicated_notification_settings.rb b/db/migrate/20160603180330_remove_duplicated_notification_settings.rb
new file mode 100644
index 0000000000000000000000000000000000000000..c2fcac4c53d9cb62d531577e9626c3dbe4e4dab2
--- /dev/null
+++ b/db/migrate/20160603180330_remove_duplicated_notification_settings.rb
@@ -0,0 +1,7 @@
+class RemoveDuplicatedNotificationSettings < ActiveRecord::Migration
+  def up
+    execute <<-SQL
+      DELETE FROM notification_settings WHERE id NOT IN ( SELECT min_id from (SELECT MIN(id) as min_id FROM notification_settings GROUP BY user_id, source_type, source_id) as dups )
+    SQL
+  end
+end
diff --git a/db/migrate/20160603182247_add_index_to_notification_settings.rb b/db/migrate/20160603182247_add_index_to_notification_settings.rb
new file mode 100644
index 0000000000000000000000000000000000000000..06462042b09d7e993a3b7cd27bdc810a0d939aa1
--- /dev/null
+++ b/db/migrate/20160603182247_add_index_to_notification_settings.rb
@@ -0,0 +1,9 @@
+class AddIndexToNotificationSettings < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  def change
+    add_concurrent_index :notification_settings, [:user_id, :source_id, :source_type], { unique: true, name: "index_notifications_on_user_id_and_source_id_and_source_type" }
+  end
+end
diff --git a/lib/gitlab/database/migration_helpers.rb b/lib/gitlab/database/migration_helpers.rb
index fd14234c5581b20284bc4f35d2c2333d2d28ad02..b88e50748f65a2a9e1b70653874fc3915bdbe964 100644
--- a/lib/gitlab/database/migration_helpers.rb
+++ b/lib/gitlab/database/migration_helpers.rb
@@ -19,7 +19,11 @@ module Gitlab
         end
 
         if Database.postgresql?
-          args << { algorithm: :concurrently }
+          if args[2].present?
+            args[2].merge!({ algorithm: :concurrently })
+          else
+            args << { algorithm: :concurrently }
+          end
         end
 
         add_index(*args)