diff --git a/changelogs/unreleased/sh-fix-issue-38246.yml b/changelogs/unreleased/sh-fix-issue-38246.yml
new file mode 100644
index 00000000000..8a127559fbb
--- /dev/null
+++ b/changelogs/unreleased/sh-fix-issue-38246.yml
@@ -0,0 +1,5 @@
+---
+title: Fix duplicate key errors in PostDeployMigrateUserExternalMailData migration
+merge_request:
+author:
+type: fixed
diff --git a/db/migrate/20170828135939_migrate_user_external_mail_data.rb b/db/migrate/20170828135939_migrate_user_external_mail_data.rb
index 592e141b7e6..395181a3b22 100644
--- a/db/migrate/20170828135939_migrate_user_external_mail_data.rb
+++ b/db/migrate/20170828135939_migrate_user_external_mail_data.rb
@@ -33,7 +33,7 @@ class MigrateUserExternalMailData < ActiveRecord::Migration
           SELECT true
           FROM user_synced_attributes_metadata
           WHERE user_id = users.id
-          AND provider = users.email_provider
+          AND provider = users.email_provider OR (provider IS NULL AND users.email_provider IS NULL)
         )
         AND id BETWEEN #{start_id} AND #{end_id}
       EOF
diff --git a/db/post_migrate/20170828170502_post_deploy_migrate_user_external_mail_data.rb b/db/post_migrate/20170828170502_post_deploy_migrate_user_external_mail_data.rb
index fefd931e5d2..a475b242921 100644
--- a/db/post_migrate/20170828170502_post_deploy_migrate_user_external_mail_data.rb
+++ b/db/post_migrate/20170828170502_post_deploy_migrate_user_external_mail_data.rb
@@ -33,7 +33,7 @@ class PostDeployMigrateUserExternalMailData < ActiveRecord::Migration
           SELECT true
           FROM user_synced_attributes_metadata
           WHERE user_id = users.id
-          AND provider = users.email_provider
+          AND provider = users.email_provider OR (provider IS NULL AND users.email_provider IS NULL)
         )
         AND id BETWEEN #{start_id} AND #{end_id}
       EOF