diff --git a/addons/web/static/src/views/kanban/kanban_renderer.js b/addons/web/static/src/views/kanban/kanban_renderer.js
index e3ad7aaf991..650030545f9 100644
--- a/addons/web/static/src/views/kanban/kanban_renderer.js
+++ b/addons/web/static/src/views/kanban/kanban_renderer.js
@@ -217,7 +217,7 @@ export class KanbanRenderer extends Component {
                 .sort((a, b) => (a.value && !b.value ? 1 : !a.value && b.value ? -1 : 0))
                 .map((group, i) => ({
                     group,
-                    key: `group_key_${isNull(group.value) ? i : String(group.value)}`,
+                    key: isNull(group.value) ? `group_key_${i}` : String(group.value),
                 }));
         } else {
             return list.records.map((record) => ({ record, key: record.id }));
diff --git a/addons/web/static/tests/views/kanban_view_tests.js b/addons/web/static/tests/views/kanban_view_tests.js
index a7f77960c13..104c1e29937 100644
--- a/addons/web/static/tests/views/kanban_view_tests.js
+++ b/addons/web/static/tests/views/kanban_view_tests.js
@@ -12061,4 +12061,59 @@ QUnit.module("Views", (hooks) => {
 
         assert.deepEqual(getCardTexts(), ["1", "3", "4", "2"]);
     });
+
+    QUnit.test("group key in foreach cannot be a duplicate", async function (assert) {
+        serverData.models.product.records = [
+            {
+                id: 1,
+                name: "Product with id 1",
+            },
+        ];
+
+        serverData.models.partner.records = [
+            {
+                id: 1,
+                name: "Partner 1",
+                product_id: 1,
+            },
+        ];
+
+        await makeView({
+            type: "kanban",
+            resModel: "partner",
+            serverData,
+            arch: /* xml */ `
+                <kanban>
+                    <templates>
+                        <div t-name="kanban-box">
+                            <field name="name" />
+                        </div>
+                    </templates>
+                </kanban>
+            `,
+            groupBy: ["product_id"],
+            async mockRPC(route, args, performRPC) {
+                if (args.method === "web_read_group") {
+                    const result = await performRPC(route, args);
+                    result.groups = [
+                        ...result.groups,
+                        {
+                            // Add an empty and valueless group, will result in foreach key group_key_0
+                            __domain: [["product_id", "=", null]],
+                            __fold: false,
+                        },
+                        {
+                            // Add an empty and valueless group, will result in foreach key group_key_1
+                            __domain: [["product_id", "=", null]],
+                            __fold: false,
+                        },
+                    ];
+                    result.length = 2;
+                    return result;
+                }
+            },
+        });
+        assert.strictEqual(target.querySelectorAll(".o_kanban_group").length, 3);
+        assert.strictEqual(target.querySelectorAll(".o_kanban_record").length, 1);
+    });
 });