diff --git a/htdocs/install/mysql/migration/18.0.0-19.0.0.sql b/htdocs/install/mysql/migration/18.0.0-19.0.0.sql
index add4fa862cd..5f45521ec9b 100644
--- a/htdocs/install/mysql/migration/18.0.0-19.0.0.sql
+++ b/htdocs/install/mysql/migration/18.0.0-19.0.0.sql
@@ -113,3 +113,9 @@ UPDATE llx_societe_account SET site = 'dolibarr_website' WHERE fk_website > 0 AN
 ALTER TABLE llx_societe_account MODIFY COLUMN site varchar(128) NOT NULL;
 
 ALTER TABLE llx_accounting_account MODIFY COLUMN pcg_type varchar(32);
+
+-- Drop the composite unique index that exists on llx_links to rebuild a new one with objecttype included.
+-- The old design did not allow same label on different object with same id.
+-- VMYSQL4.1 DROP INDEX uk_links on llx_links;
+-- VPGSQL8.2 DROP INDEX uk_links;
+ALTER TABLE llx_links ADD UNIQUE INDEX uk_links (objectid, objecttype,label);
\ No newline at end of file
diff --git a/htdocs/install/mysql/tables/llx_links.key.sql b/htdocs/install/mysql/tables/llx_links.key.sql
index 34c5e157664..444c264571a 100644
--- a/htdocs/install/mysql/tables/llx_links.key.sql
+++ b/htdocs/install/mysql/tables/llx_links.key.sql
@@ -18,5 +18,5 @@
 -- Linked files
 -- ========================================================================
 
-ALTER TABLE llx_links ADD UNIQUE INDEX uk_links (objectid,label);
+ALTER TABLE llx_links ADD UNIQUE INDEX uk_links (objectid, objecttype, label);