diff --git a/modules/ppcp-wc-gateway/src/Helper/PayUponInvoiceHelper.php b/modules/ppcp-wc-gateway/src/Helper/PayUponInvoiceHelper.php
index b91eca8a0..d84b67cc4 100644
--- a/modules/ppcp-wc-gateway/src/Helper/PayUponInvoiceHelper.php
+++ b/modules/ppcp-wc-gateway/src/Helper/PayUponInvoiceHelper.php
@@ -9,6 +9,7 @@ declare( strict_types=1 );
 
 namespace WooCommerce\PayPalCommerce\WcGateway\Helper;
 
+use WC_Customer;
 use WC_Order;
 use WC_Order_Item_Product;
 use WooCommerce\PayPalCommerce\WcGateway\Exception\NotFoundException;
@@ -48,6 +49,7 @@ class PayUponInvoiceHelper {
 	 * Checks whether checkout is ready for PUI.
 	 *
 	 * @return bool
+	 * @psalm-suppress RedundantConditionGivenDocblockType
 	 */
 	public function is_checkout_ready_for_pui(): bool {
 		$gateway_settings = get_option( 'woocommerce_ppcp-pay-upon-invoice-gateway_settings' );
@@ -55,6 +57,10 @@ class PayUponInvoiceHelper {
 			return false;
 		}
 
+		if ( ! WC()->customer instanceof WC_Customer ) {
+			return false;
+		}
+
 		// phpcs:ignore WordPress.Security.NonceVerification.Missing
 		$billing_country = WC()->customer->get_billing_country();
 		if ( empty( $billing_country ) || 'DE' !== $billing_country ) {