diff --git a/frappe/public/js/frappe/ui/sort_selector.js b/frappe/public/js/frappe/ui/sort_selector.js
index 8c87f21656..ef19905015 100644
--- a/frappe/public/js/frappe/ui/sort_selector.js
+++ b/frappe/public/js/frappe/ui/sort_selector.js
@@ -163,7 +163,7 @@ frappe.ui.SortSelector = class SortSelector {
 
 		// set default
 		this.sort_by = this.args.sort_by;
-		this.sort_order = this.args.sort_order;
+		this.sort_order = this.args.sort_order = this.args.sort_order.toLowerCase();
 	}
 	get_meta_sort_field() {
 		var meta = frappe.get_meta(this.doctype);