diff --git a/htdocs/fourn/class/fournisseur.facture.class.php b/htdocs/fourn/class/fournisseur.facture.class.php
index eebb2b95b512c..e9e669a3ad761 100644
--- a/htdocs/fourn/class/fournisseur.facture.class.php
+++ b/htdocs/fourn/class/fournisseur.facture.class.php
@@ -2881,7 +2881,9 @@ public function getNextNumRef($soc, $mode = 'next')
 			$dir = dol_buildpath($reldir."core/modules/supplier_invoice/");
 
 			// Load file with numbering class (if found)
-			$mybool |= @include_once $dir.$file;
+			// BACKPORT V20 from e19a60cd6237355fe1f8cbaf7039c6678002ac8f
+			$mybool = ((bool) @include_once $dir.$file) || $mybool;
+			// END BACKPORT
 		}
 
 		if ($mybool === false) {