diff --git a/assets/js/src/tracking.js b/assets/js/src/tracking.js
index 63329121..56e0a7ec 100644
--- a/assets/js/src/tracking.js
+++ b/assets/js/src/tracking.js
@@ -104,8 +104,19 @@ export const trackCheckoutStep =
 			return;
 		}
 
+		// compatibility-code "WC >= 8.1" -- The data structure of `storeCart` was (accidentally) changed.
+		if ( ! storeCart.hasOwnProperty( 'cartTotals' ) ) {
+			storeCart = {
+				cartCoupons: storeCart.coupons,
+				cartItems: storeCart.items,
+				cartTotals: storeCart.totals,
+			};
+		}
+
 		trackEvent( step === 0 ? 'begin_checkout' : 'checkout_progress', {
-			items: storeCart.cartItems.map( getProductFieldObject ),
+			items: storeCart.cartItems.map( ( item ) =>
+				getProductFieldObject( item, item.quantity )
+			),
 			coupon: storeCart.cartCoupons[ 0 ]?.code || '',
 			currency: storeCart.cartTotals.currency_code,
 			value: formatPrice(