diff --git a/attachment_preview/__manifest__.py b/attachment_preview/__manifest__.py
index 887d5b61..7f3ac68a 100644
--- a/attachment_preview/__manifest__.py
+++ b/attachment_preview/__manifest__.py
@@ -20,6 +20,7 @@
             "attachment_preview/static/src/js/mail_models/attachment_card.esm.js",
             "attachment_preview/static/src/js/mail_models/attachment_list.esm.js",
             "attachment_preview/static/src/js/web_views/binary_field.esm.js",
+            "attachment_preview/static/src/js/web_views/form_controller.esm.js",
             "attachment_preview/static/src/js/web_views/form_renderer.esm.js",
             "attachment_preview/static/src/scss/attachment_preview.scss",
             "attachment_preview/static/src/xml/attachment_preview.xml",
diff --git a/attachment_preview/static/src/js/web_views/form_controller.esm.js b/attachment_preview/static/src/js/web_views/form_controller.esm.js
new file mode 100644
index 00000000..fece812a
--- /dev/null
+++ b/attachment_preview/static/src/js/web_views/form_controller.esm.js
@@ -0,0 +1,12 @@
+/** @odoo-module **/
+import {FormController} from "@web/views/form/form_controller";
+import {patch} from "@web/core/utils/patch";
+
+patch(FormController.prototype, "attachment_preview.FormController", {
+    /* Defined in addons/mail/static/src/views/form/form_controller.js.
+     * This method controls Odoo's default attachment sidebar, which only shows
+     * up based on screen size. ➔ Superseded by this module; we disable it. */
+    hasAttachmentViewer() {
+        return false;
+    },
+});