diff --git a/htdocs/core/lib/modulebuilder.lib.php b/htdocs/core/lib/modulebuilder.lib.php
index eff2df330a2..67d57193729 100644
--- a/htdocs/core/lib/modulebuilder.lib.php
+++ b/htdocs/core/lib/modulebuilder.lib.php
@@ -411,7 +411,7 @@ function rebuildObjectSql($destdir, $module, $objectname, $newmask, $readdir = '
 		foreach ($object->fields as $key => $val) {
 			$i++;
 			if (!empty($val['index'])) {
-				$texttoinsert .= "ALTER TABLE llx_".strtolower($module).'_'.strtolower($objectname)." ADD INDEX idx_".strtolower($module).'_'.strtolower($objectname)."_".$key." (".$key.");";
+				$texttoinsert .= "ALTER TABLE llx_".strtolower($module).'_'.strtolower($objectname)." ADD ".($key == 'ref' ? "UNIQUE INDEX uk_" : "INDEX idx_").strtolower($module).'_'.strtolower($objectname)."_".$key." (".$key.($key == 'ref' && array_key_exists('entity', $object->fields) ? ", entity" : "").");";
 				$texttoinsert .= "\n";
 			}
 			if (!empty($val['foreignkey'])) {