diff --git a/includes/rules-shipping-method.php b/includes/rules-shipping-method.php
index 120ab72135846c07cba12c3822e992f6819707df..f44293cc928b77a1eef0fc87d17710eefa2df95f 100644
--- a/includes/rules-shipping-method.php
+++ b/includes/rules-shipping-method.php
@@ -142,7 +142,7 @@ class Shipping_by_Rules extends WC_Shipping_Method {
 	 * @param mixed $package
 	 * @return void
 	 */
-	public function calculate_shipping( $package ) {
+	public function calculate_shipping( $package = array()) {
 		$methods = $this->helper->get_rule_shipping_methods();
 		foreach ($methods as $method) {