diff --git a/htdocs/modulebuilder/template/sql/llx_mymodule_myobject_extrafields.key.sql b/htdocs/modulebuilder/template/sql/llx_mymodule_myobject_extrafields.key.sql
index 4c005e9d170..b421e6304bd 100644
--- a/htdocs/modulebuilder/template/sql/llx_mymodule_myobject_extrafields.key.sql
+++ b/htdocs/modulebuilder/template/sql/llx_mymodule_myobject_extrafields.key.sql
@@ -15,5 +15,5 @@
 
 
 -- BEGIN MODULEBUILDER INDEXES
-ALTER TABLE llx_mymodule_myobject_extrafields ADD INDEX idx_myobject_fk_object(fk_object);
+ALTER TABLE llx_mymodule_myobject_extrafields ADD UNIQUE INDEX idx_myobject_fk_object(fk_object);
 -- END MODULEBUILDER INDEXES