diff --git a/htdocs/install/mysql/migration/3.3.0-3.4.0.sql b/htdocs/install/mysql/migration/3.3.0-3.4.0.sql
index 6a611372690..8f098876062 100755
--- a/htdocs/install/mysql/migration/3.3.0-3.4.0.sql
+++ b/htdocs/install/mysql/migration/3.3.0-3.4.0.sql
@@ -17,6 +17,7 @@
 -- -- VPGSQL8.2 DELETE FROM llx_usergroup_user      WHERE fk_user      NOT IN (SELECT rowid from llx_user);
 -- -- VMYSQL4.1 DELETE FROM llx_usergroup_user      WHERE fk_usergroup NOT IN (SELECT rowid from llx_usergroup);
 
+
 create table llx_adherent_type_extrafields
 (
   rowid                     integer AUTO_INCREMENT PRIMARY KEY,
@@ -49,7 +50,13 @@ alter table llx_contratdet add column buy_price_ht double(24,8) DEFAULT 0 after
 alter table llx_extrafields add column param text after pos;
 
 -- numbering on supplier invoice
-alter table llx_facture_fourn add column ref varchar(30) NOT NULL after rowid;
+ALTER TABLE llx_facture_fourn ADD COLUMN ref varchar(30) after rowid;
+ALTER TABLE llx_facture_fourn MODIFY COLUMN ref varchar(30);
+ALTER TABLE llx_facture_fourn DROP INDEX uk_facture_fourn;
+ALTER TABLE llx_facture_fourn DROP INDEX uk_facture_fourn_ref;
+UPDATE llx_facture_fourn set ref = NULL where ref = '';
+ALTER TABLE llx_facture_fourn ADD UNIQUE INDEX uk_facture_fourn_ref (ref, entity);
+ALTER TABLE llx_facture_fourn ADD UNIQUE INDEX uk_facture_fourn_ref_supplier (ref_supplier, fk_soc, entity);
 
 
 alter table llx_propal   CHANGE COLUMN fk_adresse_livraison fk_delivery_address integer;
diff --git a/htdocs/install/mysql/tables/llx_facture_fourn.key.sql b/htdocs/install/mysql/tables/llx_facture_fourn.key.sql
index 481974a6c4d..7130640a9f0 100644
--- a/htdocs/install/mysql/tables/llx_facture_fourn.key.sql
+++ b/htdocs/install/mysql/tables/llx_facture_fourn.key.sql
@@ -17,8 +17,8 @@
 --
 -- ============================================================================
 
-
-ALTER TABLE llx_facture_fourn ADD UNIQUE INDEX uk_facture_fourn_ref (ref, fk_soc, entity);
+ALTER TABLE llx_facture_fourn ADD UNIQUE INDEX uk_facture_fourn_ref (ref, entity);
+ALTER TABLE llx_facture_fourn ADD UNIQUE INDEX uk_facture_fourn_ref_supplier (ref_supplier, fk_soc, entity);
 
 ALTER TABLE llx_facture_fourn ADD INDEX idx_facture_fourn_date_lim_reglement (date_lim_reglement);