diff --git a/htdocs/install/mysql/migration/2.9.0-3.0.0.sql b/htdocs/install/mysql/migration/2.9.0-3.0.0.sql
index 085d0b1db75..183f2ac179f 100644
--- a/htdocs/install/mysql/migration/2.9.0-3.0.0.sql
+++ b/htdocs/install/mysql/migration/2.9.0-3.0.0.sql
@@ -160,3 +160,6 @@ UPDATE llx_documentmodel set type='order_supplier' WHERE type='supplier_order';
 UPDATE llx_c_type_contact set element='invoice_supplier' WHERE element='facture_fourn';
 UPDATE llx_c_type_contact set module='invoice_supplier' WHERE module='supplier_invoice';
 UPDATE llx_c_type_contact set module='order_supplier' WHERE module='supplier_order';
+
+ALTER TABLE llx_facturedet DROP INDEX uk_fk_remise_except;
+ALTER TABLE llx_facturedet ADD UNIQUE INDEX uk_fk_remise_except (fk_remise_except, fk_facture);
diff --git a/htdocs/install/mysql/tables/llx_facturedet.key.sql b/htdocs/install/mysql/tables/llx_facturedet.key.sql
index 44df288c94d..bc2d8976966 100644
--- a/htdocs/install/mysql/tables/llx_facturedet.key.sql
+++ b/htdocs/install/mysql/tables/llx_facturedet.key.sql
@@ -23,5 +23,5 @@
 -- V4 DELETE llx_facturedet FROM llx_facturedet LEFT JOIN llx_facture ON llx_facturedet.fk_facture = llx_facture.rowid WHERE llx_facture.rowid IS NULL;
 
 ALTER TABLE llx_facturedet ADD INDEX idx_facturedet_fk_facture (fk_facture);
-ALTER TABLE llx_facturedet ADD UNIQUE INDEX uk_fk_remise_except (fk_remise_except);
+ALTER TABLE llx_facturedet ADD UNIQUE INDEX uk_fk_remise_except (fk_remise_except, fk_facture);
 ALTER TABLE llx_facturedet ADD CONSTRAINT fk_facturedet_fk_facture FOREIGN KEY (fk_facture) REFERENCES llx_facture (rowid);