diff --git a/htdocs/core/js/lib_foot.js.php b/htdocs/core/js/lib_foot.js.php
index ae0de6ad0cb..5ed7dfb2eb1 100644
--- a/htdocs/core/js/lib_foot.js.php
+++ b/htdocs/core/js/lib_foot.js.php
@@ -128,7 +128,7 @@ if (empty($conf->dol_no_mouse_hover)) {
 print '
 	jQuery(".classfortooltiponclicktext").dialog({
 		closeOnEscape: true, classes: { "ui-dialog": "highlight" },
-		maxHeight: window.innerHeight-60, width: '.($conf->browser->layout == 'phone' ? max($_SESSION['dol_screenwidth'] - 20, 320) : 700).',
+		maxHeight: window.innerHeight-60, width: '.($conf->browser->layout == 'phone' ? max((empty($_SESSION['dol_screenwidth']) ? 0 : $_SESSION['dol_screenwidth']) - 20, 320) : 700).',
 		modal: true,
 		autoOpen: false
 	}).css("z-index: 5000");