diff --git a/htdocs/eventorganization/class/conferenceorboothattendee.class.php b/htdocs/eventorganization/class/conferenceorboothattendee.class.php
index f6e4bff74cd..f30196c2ef3 100644
--- a/htdocs/eventorganization/class/conferenceorboothattendee.class.php
+++ b/htdocs/eventorganization/class/conferenceorboothattendee.class.php
@@ -969,7 +969,7 @@ class ConferenceOrBoothAttendee extends CommonObject
 				$dir = dol_buildpath($reldir."core/modules/eventorganization/");
 
 				// Load file with numbering class (if found)
-				$mybool |= @include_once $dir.$file;
+				$mybool = ((bool) @include_once $dir.$file) || $mybool;
 			}
 
 			if ($mybool === false) {