diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index bce43c8c5d8..e24b5ba4c7f 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -3463,12 +3463,21 @@ function dol_htmloutput_events($mesgs=array(),$errors=array(),$warnings=array())
 	if (isset($_SESSION['dol_events']))
 	{
 		if (is_array($mesgs) && isset($_SESSION['dol_events']['mesgs'])) {
+			if (! is_array($_SESSION['dol_events']['mesgs'])) {
+				$_SESSION['dol_events']['mesgs']=array($_SESSION['dol_events']['mesgs']); // For backward compatibility
+			}
 			$mesgs = array_merge($mesgs, $_SESSION['dol_events']['mesgs']);
 		}
 		if (is_array($errors) && isset($_SESSION['dol_events']['errors'])) {
+			if (! is_array($_SESSION['dol_events']['errors'])) {
+				$_SESSION['dol_events']['errors']=array($_SESSION['dol_events']['errors']); // For backward compatibility
+			}
 			$errors = array_merge($errors, $_SESSION['dol_events']['errors']);
 		}
 		if (is_array($warnings) && isset($_SESSION['dol_events']['warnings'])) {
+			if (! is_array($_SESSION['dol_events']['warnings'])) {
+				$_SESSION['dol_events']['warnings']=array($_SESSION['dol_events']['warnings']); // For backward compatibility
+			}
 			$warnings = array_merge($warnings, $_SESSION['dol_events']['warnings']);
 		}