diff --git a/addons/web/static/src/legacy/js/views/pivot/pivot_model.js b/addons/web/static/src/legacy/js/views/pivot/pivot_model.js
index 72296444aa4..6fc3f6bc136 100644
--- a/addons/web/static/src/legacy/js/views/pivot/pivot_model.js
+++ b/addons/web/static/src/legacy/js/views/pivot/pivot_model.js
@@ -719,7 +719,11 @@ var PivotModel = AbstractModel.extend({
         values.slice(0, values.length - 1).forEach(function (value) {
             tree = tree.directSubTrees.get(value);
         });
-        tree.directSubTrees.set(values[values.length - 1], {
+        const value = values[values.length - 1];
+        if (tree.directSubTrees.has(value)) {
+            return;
+        }
+        tree.directSubTrees.set(value, {
             root: {
                 labels: labels,
                 values: values,
diff --git a/addons/web/static/src/views/pivot/pivot_model.js b/addons/web/static/src/views/pivot/pivot_model.js
index fe30557458b..fb3b353773d 100644
--- a/addons/web/static/src/views/pivot/pivot_model.js
+++ b/addons/web/static/src/views/pivot/pivot_model.js
@@ -779,7 +779,11 @@ export class PivotModel extends Model {
         values.slice(0, values.length - 1).forEach(function (value) {
             tree = tree.directSubTrees.get(value);
         });
-        tree.directSubTrees.set(values[values.length - 1], {
+        const value = values[values.length - 1];
+        if (tree.directSubTrees.has(value)) {
+            return;
+        }
+        tree.directSubTrees.set(value, {
             root: {
                 labels: labels,
                 values: values,
diff --git a/addons/web/static/tests/legacy/views/pivot_tests.js b/addons/web/static/tests/legacy/views/pivot_tests.js
index 8a85ea42361..36ecf32b5b8 100644
--- a/addons/web/static/tests/legacy/views/pivot_tests.js
+++ b/addons/web/static/tests/legacy/views/pivot_tests.js
@@ -3434,6 +3434,70 @@ QUnit.module('Views', {
         pivot.destroy();
     });
 
+    QUnit.test('comparison with two groupbys: rows from reference period should be displayed', async function (assert) {
+        assert.expect(3);
+
+        this.data.partner.records = [
+            { id: 1, date: "2021-10-10", product_id: 1, customer: 1 },
+            { id: 2, date: "2020-10-10", product_id: 2, customer: 1 },
+        ]
+        this.data.product.records = [
+            { id: 1, display_name: "A" },
+            { id: 2, display_name: "B" },
+        ]
+        this.data.customer.records = [
+            { id: 1, display_name: "P" },
+        ]
+
+        const pivot = await createView({
+            View: PivotView,
+            model: "partner",
+            data: this.data,
+            arch: '<pivot><field name="customer" type="row"/><field name="product_id" type="row"/></pivot>',
+            archs: {
+                "partner,false,search": "<search><filter name='date' date='date'/></search>"
+            },
+        });
+
+        // compare 2021 to 2020
+        await cpHelpers.toggleFilterMenu(pivot.el);
+        await cpHelpers.toggleMenuItem(pivot.el, "Date");
+        await cpHelpers.toggleMenuItemOption(pivot.el, "Date", "2021");
+        await cpHelpers.toggleComparisonMenu(pivot.el);
+        await cpHelpers.toggleMenuItem(pivot.el, 0);
+
+        assert.strictEqual(
+            pivot.$('th').slice(0, 6).text(),
+            [
+                        "Total",
+                        "Count",
+                "2020", "2021", "Variation"
+            ].join(''),
+            "The col headers should be as expected"
+        );
+
+        assert.strictEqual(
+            pivot.$('th').slice(6).text(),
+            [
+                'Total',
+                    'P',
+                        'B',
+                        'A',
+            ].join(''),
+            "The row headers should be as expected"
+        );
+
+        const values = [
+            "1", "1", "0%",
+            "1", "1", "0%",
+            "1", "0", "-100%",
+            "0", "1", "100%",
+        ];
+        assert.strictEqual(getCurrentValues(pivot), values.join());
+
+        pivot.destroy();
+    });
+
     QUnit.test('pivot rendering with boolean field', async function (assert) {
         assert.expect(4);
 
diff --git a/addons/web/static/tests/views/pivot_view_tests.js b/addons/web/static/tests/views/pivot_view_tests.js
index f08ce150816..2ca8c08afa5 100644
--- a/addons/web/static/tests/views/pivot_view_tests.js
+++ b/addons/web/static/tests/views/pivot_view_tests.js
@@ -5335,4 +5335,60 @@ QUnit.module("Views", (hooks) => {
         // No separator should be displayed in the menu "Measures"
         assert.containsNone(pivot, ".o_cp_bottom_left .dropdown-menu div.dropdown-divider");
     });
+
+    QUnit.test(
+        "comparison with two groupbys: rows from reference period should be displayed",
+        async function (assert) {
+            assert.expect(3);
+
+            serverData.models.partner.records = [
+                { id: 1, date: "2021-10-10", product_id: 1, customer: 1 },
+                { id: 2, date: "2020-10-10", product_id: 2, customer: 1 },
+            ];
+            serverData.models.product.records = [
+                { id: 1, display_name: "A" },
+                { id: 2, display_name: "B" },
+            ];
+            serverData.models.customer.records = [{ id: 1, display_name: "P" }];
+
+            const pivot = await makeView({
+                type: "pivot",
+                resModel: "partner",
+                serverData,
+                arch: `
+                <pivot>
+                    <field name="customer" type="row"/>
+                    <field name="product_id" type="row"/>
+                </pivot>
+            `,
+                searchViewArch: `
+                <search>
+                    <filter name='date' date='date'/>
+                </search>
+            `,
+            });
+
+            // compare 2021 to 2020
+            await toggleFilterMenu(pivot);
+            await toggleMenuItem(pivot, "Date");
+            await toggleMenuItemOption(pivot, "Date", "2021");
+            await toggleComparisonMenu(pivot);
+            await toggleMenuItem(pivot, 0);
+
+            assert.deepEqual(
+                [...pivot.el.querySelectorAll("th")].slice(0, 6).map((el) => el.innerText),
+                ["", "Total", "Count", "2020", "2021", "Variation"],
+                "The col headers should be as expected"
+            );
+
+            assert.deepEqual(
+                [...pivot.el.querySelectorAll("th")].slice(6).map((el) => el.innerText),
+                ["Total", "P", "B", "A"],
+                "The row headers should be as expected"
+            );
+
+            const values = ["1", "1", "0%", "1", "1", "0%", "1", "0", "-100%", "0", "1", "100%"];
+            assert.strictEqual(getCurrentValues(pivot), values.join());
+        }
+    );
 });