diff --git a/packages/mermaid/src/diagrams/gantt/ganttDb.js b/packages/mermaid/src/diagrams/gantt/ganttDb.js
index d79a57fc2..da838f839 100644
--- a/packages/mermaid/src/diagrams/gantt/ganttDb.js
+++ b/packages/mermaid/src/diagrams/gantt/ganttDb.js
@@ -67,7 +67,7 @@ export const clear = function () {
   lastOrder = 0;
   links = {};
   commonClear();
-  weekday = undefined;
+  weekday = 'sunday';
 };
 
 export const setAxisFormat = function (txt) {