diff --git a/db/docs/abuse_report_assignees.yml b/db/docs/abuse_report_assignees.yml
index 863609a0cae93325f9ae2b6d50793a07ea19ab33..2b887ab05057fc4a3a6c58b3b0497346adf0b023 100644
--- a/db/docs/abuse_report_assignees.yml
+++ b/db/docs/abuse_report_assignees.yml
@@ -7,6 +7,7 @@ feature_categories:
 description: Stores information linking abuse reports and users (assignee)
 introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/134240
 milestone: '16.7'
-gitlab_schema: gitlab_main
+gitlab_schema: gitlab_main_org
+sharding_key:
+  organization_id: organizations
 table_size: small
-sharding_key_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/553428
diff --git a/db/migrate/20250924121403_remove_default_from_abuse_report_assignees_organization_id.rb b/db/migrate/20250924121403_remove_default_from_abuse_report_assignees_organization_id.rb
new file mode 100644
index 0000000000000000000000000000000000000000..73a2c7b76ef57ebc773910eba332c783ee437e2b
--- /dev/null
+++ b/db/migrate/20250924121403_remove_default_from_abuse_report_assignees_organization_id.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class RemoveDefaultFromAbuseReportAssigneesOrganizationId < Gitlab::Database::Migration[2.3]
+  milestone '18.5'
+
+  def change
+    change_column_default(:abuse_report_assignees, :organization_id, from: 1, to: nil)
+  end
+end
diff --git a/db/schema_migrations/20250924121403 b/db/schema_migrations/20250924121403
new file mode 100644
index 0000000000000000000000000000000000000000..5fad6b8706f6fbac1a7c1ba2202bdec6d5c976fb
--- /dev/null
+++ b/db/schema_migrations/20250924121403
@@ -0,0 +1 @@
+2a086dc954b59b5dc5b1ad0a4894882c52d726ac8a5bb1c446a7085dd080c7cd
\ No newline at end of file
diff --git a/db/structure.sql b/db/structure.sql
index c4c3875155a13d9dd11a5d635758c70ab1c74b62..4bc4977e4961e161f73da1c0437bcf844f29153b 100644
--- a/db/structure.sql
+++ b/db/structure.sql
@@ -9309,7 +9309,7 @@ CREATE TABLE abuse_report_assignees (
     abuse_report_id bigint NOT NULL,
     created_at timestamp with time zone NOT NULL,
     updated_at timestamp with time zone NOT NULL,
-    organization_id bigint DEFAULT 1 NOT NULL
+    organization_id bigint NOT NULL
 );
 
 CREATE SEQUENCE abuse_report_assignees_id_seq
diff --git a/spec/lib/gitlab/database/sharding_key_spec.rb b/spec/lib/gitlab/database/sharding_key_spec.rb
index f3da05caf6af29827ba44146f9fdee53c0b9bff9..0230c7025062184554438fabc6de7bc1fd83559b 100644
--- a/spec/lib/gitlab/database/sharding_key_spec.rb
+++ b/spec/lib/gitlab/database/sharding_key_spec.rb
@@ -318,7 +318,6 @@
       "abuse_report_labels" => "https://gitlab.com/gitlab-org/gitlab/-/issues/553427",
       "abuse_report_events" => "https://gitlab.com/gitlab-org/gitlab/-/issues/553429",
       "abuse_events" => "https://gitlab.com/gitlab-org/gitlab/-/issues/553427",
-      "abuse_report_assignees" => "https://gitlab.com/gitlab-org/gitlab/-/issues/553428",
       "labels" => "https://gitlab.com/gitlab-org/gitlab/-/issues/563889",
       "notes" => "https://gitlab.com/gitlab-org/gitlab/-/issues/569521",
       "notes_archived" => "https://gitlab.com/gitlab-org/gitlab/-/issues/569521",