diff --git a/addons/mass_mailing/__manifest__.py b/addons/mass_mailing/__manifest__.py
index 970665fcc0e..a8be759106a 100644
--- a/addons/mass_mailing/__manifest__.py
+++ b/addons/mass_mailing/__manifest__.py
@@ -130,6 +130,7 @@
             'mass_mailing/static/src/snippets/s_showcase/options.js',
             'mass_mailing/static/src/snippets/s_rating/options.js',
             'mass_mailing/static/tests/mass_mailing_html_tests.js',
+            'mass_mailing/static/tests/mailing_mailing_view_form_tests.js',
         ],
     },
     'license': 'LGPL-3',
diff --git a/addons/mass_mailing/static/src/js/mailing_mailing_view_form_full_width.js b/addons/mass_mailing/static/src/js/mailing_mailing_view_form_full_width.js
index 3f0d2b75cd0..d60cbf5a329 100644
--- a/addons/mass_mailing/static/src/js/mailing_mailing_view_form_full_width.js
+++ b/addons/mass_mailing/static/src/js/mailing_mailing_view_form_full_width.js
@@ -30,6 +30,7 @@ export class MassMailingFullWidthViewController extends formView.Controller {
         });
         onWillUnmount(() => {
             $('.o_content').off('.repositionMailingEditorSidebar');
+            this._resizeObserver.disconnect();
         });
     }
     //--------------------------------------------------------------------------
diff --git a/addons/mass_mailing/static/tests/mailing_mailing_view_form_tests.js b/addons/mass_mailing/static/tests/mailing_mailing_view_form_tests.js
new file mode 100644
index 00000000000..5eb0e999600
--- /dev/null
+++ b/addons/mass_mailing/static/tests/mailing_mailing_view_form_tests.js
@@ -0,0 +1,71 @@
+/** @odoo-module **/
+
+import { setupViewRegistries } from "@web/../tests/views/helpers";
+import { patchWithCleanup } from "@web/../tests/helpers/utils";
+import { createWebClient, doAction } from "@web/../tests/webclient/helpers";
+import { MassMailingFullWidthViewController } from "@mass_mailing/js/mailing_mailing_view_form_full_width";
+
+let serverData;
+
+QUnit.module("mass_mailing", {}, function () {
+    QUnit.module("MassMailingFullWidthViewController", (hooks) => {
+        hooks.beforeEach(() => {
+            serverData = {
+                models: {
+                    partner: {
+                        fields: {
+                            display_name: { string: "Displayed name", type: "char" },
+                        },
+                    },
+                },
+
+                actions: {
+                    1: {
+                        id: 1,
+                        name: "test",
+                        res_model: "partner",
+                        type: "ir.actions.act_window",
+                        views: [[false, "form"]],
+                    },
+                    2: {
+                        id: 2,
+                        name: "test",
+                        res_model: "partner",
+                        type: "ir.actions.act_window",
+                        views: [[false, "list"]],
+                    },
+                },
+
+                views: {
+                    "partner,false,form": `<form js_class="mailing_mailing_view_form_full_width">
+                        <field name="display_name"/>
+                    </form>`,
+                    "partner,false,list": `<tree><field name="display_name"/></tree>`,
+                    "partner,false,search": `<search/>`,
+                },
+            };
+
+            setupViewRegistries();
+        });
+
+        QUnit.test("unregister ResizeObserver on unmount", async (assert) => {
+            patchWithCleanup(MassMailingFullWidthViewController.prototype, {
+                setup() {
+                    this._super();
+                    patchWithCleanup(this._resizeObserver, {
+                        disconnect() {
+                            assert.step("disconnect");
+                            return this._super(...arguments);
+                        },
+                    });
+                },
+            });
+
+            const webClient = await createWebClient({ serverData });
+            await doAction(webClient, 1);
+            assert.verifySteps([]);
+            await doAction(webClient, 2);
+            assert.verifySteps(["disconnect"]);
+        });
+    });
+});