diff --git a/frappe/database/mariadb/schema.py b/frappe/database/mariadb/schema.py
index 3465058631..73a92dfa4a 100644
--- a/frappe/database/mariadb/schema.py
+++ b/frappe/database/mariadb/schema.py
@@ -85,7 +85,7 @@ class MariaDBTable(DBTable):
 			if not frappe.db.get_column_index(self.table_name, col.fieldname, unique=False)
 		]
 
-		if self.meta.sort_field == "modified" and frappe.db.get_column_index(
+		if self.meta.sort_field == "modified" and not frappe.db.get_column_index(
 			self.table_name, "modified", unique=False
 		):
 			add_index_query.append("ADD INDEX `modified`(`modified`)")