diff --git a/addons/website_sale/static/src/js/website_sale.js b/addons/website_sale/static/src/js/website_sale.js
index cdd0dcf56ae..6d25860a9af 100644
--- a/addons/website_sale/static/src/js/website_sale.js
+++ b/addons/website_sale/static/src/js/website_sale.js
@@ -372,21 +372,11 @@ publicWidget.registry.WebsiteSale = publicWidget.Widget.extend(VariantMixin, car
             if (!data.cart_quantity) {
                 return window.location = '/shop/cart';
             }
-            wSaleUtils.updateCartNavBar(data);
             $input.val(data.quantity);
             $('.js_quantity[data-line-id='+line_id+']').val(data.quantity).text(data.quantity);
 
-            if (data.warning) {
-                var cart_alert = $('.oe_cart').parent().find('#data_warning');
-                if (cart_alert.length === 0) {
-                    $('.oe_cart').prepend('<div class="alert alert-danger alert-dismissable" role="alert" id="data_warning">'+
-                            '<button type="button" class="btn-close" data-bs-dismiss="alert" aria-hidden="true"></button> ' + data.warning + '</div>');
-                }
-                else {
-                    cart_alert.html('<button type="button" class="btn-close" data-bs-dismiss="alert" aria-hidden="true"></button> ' + data.warning);
-                }
-                $input.val(data.quantity);
-            }
+            wSaleUtils.updateCartNavBar(data);
+            wSaleUtils.showWarning(data.warning);
         });
     },
     /**
diff --git a/addons/website_sale/static/src/js/website_sale_utils.js b/addons/website_sale/static/src/js/website_sale_utils.js
index ba5cdc842c7..75f8ae80a4b 100644
--- a/addons/website_sale/static/src/js/website_sale_utils.js
+++ b/addons/website_sale/static/src/js/website_sale_utils.js
@@ -95,22 +95,48 @@ function animateClone($cart, $elem, offsetTop, offsetLeft) {
  * @param {Object} data
  */
 function updateCartNavBar(data) {
-    var $qtyNavBar = $(".my_cart_quantity");
-    _.each($qtyNavBar, function (qty) {
-        var $qty = $(qty);
-        $qty.parents('li:first').removeClass('d-none');
-        $qty.addClass('o_mycart_zoom_animation').delay(300).queue(function () {
-            $(this).text(data.cart_quantity);
-            $(this).removeClass("o_mycart_zoom_animation").dequeue();
+    $(".my_cart_quantity")
+        .parents('li.o_wsale_my_cart').removeClass('d-none').end()
+        .addClass('o_mycart_zoom_animation').delay(300)
+        .queue(function () {
+            $(this)
+                .toggleClass('fa fa-warning', !data.cart_quantity)
+                .attr('title', data.warning)
+                .text(data.cart_quantity || '')
+                .removeClass('o_mycart_zoom_animation')
+                .dequeue();
         });
-    });
+
     $(".js_cart_lines").first().before(data['website_sale.cart_lines']).end().remove();
     $(".js_cart_summary").first().before(data['website_sale.short_cart_summary']).end().remove();
 }
 
+/**
+ * Displays `message` in an alert box at the top of the page if it's a
+ * non-empty string.
+ *
+ * @param {string | null} message
+ */
+function showWarning(message) {
+    if (!message) {
+        return;
+    }
+    var $page = $('.oe_website_sale');
+    var cart_alert = $page.children('#data_warning');
+    if (!cart_alert.length) {
+        cart_alert = $(
+            '<div class="alert alert-danger alert-dismissible" role="alert" id="data_warning">' +
+                '<button type="button" class="btn-close" data-bs-dismiss="alert">&times;</button> ' +
+                '<span></span>' +
+            '</div>').prependTo($page);
+    }
+    cart_alert.children('span:last-child').text(message);
+}
+
 return {
     animateClone: animateClone,
     updateCartNavBar: updateCartNavBar,
     cartHandlerMixin: cartHandlerMixin,
+    showWarning: showWarning,
 };
 });
diff --git a/addons/website_sale_wishlist/static/src/js/website_sale_wishlist.js b/addons/website_sale_wishlist/static/src/js/website_sale_wishlist.js
index dfaabb010ec..699cb590ee4 100644
--- a/addons/website_sale_wishlist/static/src/js/website_sale_wishlist.js
+++ b/addons/website_sale_wishlist/static/src/js/website_sale_wishlist.js
@@ -188,16 +188,10 @@ publicWidget.registry.ProductWishlist = publicWidget.Widget.extend(VariantMixin,
         return this._rpc({
             route: "/shop/cart/update_json",
             params: this._getCartUpdateJsonParams(productID, qty),
-        }).then(function (resp) {
-            if (resp.warning) {
-                if (! $('#data_warning').length) {
-                    $('.wishlist-section').prepend('<div class="mt16 alert alert-danger alert-dismissable" role="alert" id="data_warning"></div>');
-                }
-                var cart_alert = $('.wishlist-section').parent().find('#data_warning');
-                cart_alert.html('<button type="button" class="btn-close" data-bs-dismiss="alert" aria-hidden="true">&times;</button> ' + resp.warning);
-            }
-            sessionStorage.setItem('website_sale_cart_quantity', resp.cart_quantity);
-            $('.my_cart_quantity').html(resp.cart_quantity || '<i class="fa fa-warning" /> ');
+        }).then(function (data) {
+            sessionStorage.setItem('website_sale_cart_quantity', data.cart_quantity);
+            wSaleUtils.updateCartNavBar(data);
+            wSaleUtils.showWarning(data.warning);
         });
     },
     /**