diff --git a/addons/website/static/src/js/content/snippets.animation.js b/addons/website/static/src/js/content/snippets.animation.js
index e7b9fe37eed..a19e57b9f82 100644
--- a/addons/website/static/src/js/content/snippets.animation.js
+++ b/addons/website/static/src/js/content/snippets.animation.js
@@ -1142,7 +1142,16 @@ registry.FullScreenHeight = publicWidget.Widget.extend({
         // Doing it that way allows to considerer fixed headers, hidden headers,
         // connected users, ...
         const firstContentEl = $('#wrapwrap > main > :first-child')[0]; // first child to consider the padding-top of main
+        // When a modal is open, we remove the "modal-open" class from the body.
+        // This is because this class sets "#wrapwrap" and "<body>" to
+        // "overflow: hidden," preventing the "closestScrollable" function from
+        // correctly recognizing the scrollable element closest to the element
+        // for which the height needs to be calculated. Without this, the
+        // "mainTopPos" variable would be incorrect.
+        const modalOpen = document.body.classList.contains("modal-open");
+        document.body.classList.remove("modal-open");
         const mainTopPos = firstContentEl.getBoundingClientRect().top + $(firstContentEl.parentNode).closestScrollable()[0].scrollTop;
+        document.body.classList.toggle("modal-open", modalOpen);
         return (windowHeight - mainTopPos);
     },
 });