diff --git a/core/js/update.js b/core/js/update.js
index fd3c7a56bd6..79bf7c5ffbe 100644
--- a/core/js/update.js
+++ b/core/js/update.js
@@ -45,6 +45,7 @@
 				hasWarnings = true;
 			});
 			updateEventSource.listen('error', function(message) {
+				message = message || t('core', 'An error occurred.');
 				$('<span>').addClass('error').append(message).append('<br />').appendTo($el);
 				message = t('core', 'Please reload the page.');
 				$('<span>').addClass('error').append(message).append('<br />').appendTo($el);