diff --git a/includes/documents/abstract-wcpdf-order-document.php b/includes/documents/abstract-wcpdf-order-document.php
index 2fccdd850..6d973f05a 100644
--- a/includes/documents/abstract-wcpdf-order-document.php
+++ b/includes/documents/abstract-wcpdf-order-document.php
@@ -1405,7 +1405,8 @@ public function get_due_date(): int {
 		}
 
 		$base_date         = apply_filters( 'wpo_wcpdf_due_date_base_date', $this->order->get_date_created(), $this->type, $this );
-		$due_date_datetime = $base_date->modify( "+$due_date_days days" );
+		$due_date_datetime = clone $base_date;
+		$due_date_datetime = $due_date_datetime->modify( "+$due_date_days days" );
 
 		return apply_filters( 'wpo_wcpdf_due_date', $due_date_datetime->getTimestamp() ?? 0, $this->type, $this );
 	}