diff --git a/includes/class-wc-emails.php b/includes/class-wc-emails.php
index 16c3ffdf0a7..2a41d27ae48 100644
--- a/includes/class-wc-emails.php
+++ b/includes/class-wc-emails.php
@@ -366,12 +366,15 @@ class WC_Emails {
 	/**
 	 * Add customer details to email templates.
 	 *
-	 * @param mixed $order
+	 * @param WC_Order $order
 	 * @param bool $sent_to_admin (default: false)
 	 * @param bool $plain_text (default: false)
 	 * @return string
 	 */
 	public function customer_details( $order, $sent_to_admin = false, $plain_text = false ) {
+		if ( ! is_a( 'WC_Order', $order ) ) {
+			return;
+		}
 		$fields = array();
 
 		if ( $order->get_customer_note() ) {
@@ -386,14 +389,14 @@ class WC_Emails {
 				'label' => __( 'Email address', 'woocommerce' ),
 				'value' => wptexturize( $order->get_billing_email() ),
 			);
-	    }
+		}
 
-	    if ( $order->get_billing_phone() ) {
+		if ( $order->get_billing_phone() ) {
 			$fields['billing_phone'] = array(
 				'label' => __( 'Phone', 'woocommerce' ),
 				'value' => wptexturize( $order->get_billing_phone() ),
 			);
-	    }
+		}
 
 		$fields = array_filter( apply_filters( 'woocommerce_email_customer_details_fields', $fields, $sent_to_admin, $order ), array( $this, 'customer_detail_field_is_valid' ) );
 
@@ -408,6 +411,9 @@ class WC_Emails {
 	 * Get the email addresses.
 	 */
 	public function email_addresses( $order, $sent_to_admin = false, $plain_text = false ) {
+		if ( ! is_a( 'WC_Order', $order ) ) {
+			return;
+		}
 		if ( $plain_text ) {
 			wc_get_template( 'emails/plain/email-addresses.php', array( 'order' => $order ) );
 		} else {
diff --git a/includes/class-wc-structured-data.php b/includes/class-wc-structured-data.php
index 504427b6364..bac68582478 100644
--- a/includes/class-wc-structured-data.php
+++ b/includes/class-wc-structured-data.php
@@ -328,7 +328,7 @@ class WC_Structured_Data {
 	 * @param bool	    $plain_text    Plain text email (default: false).
 	 */
 	public function generate_order_data( $order, $sent_to_admin = false, $plain_text = false ) {
-		if ( $plain_text ) {
+		if ( $plain_text || ! is_a( $order, 'WC_Order' ) ) {
 			return;
 		}