diff --git a/addons/web/static/src/js/views/graph/graph_renderer.js b/addons/web/static/src/js/views/graph/graph_renderer.js
index da5709a6261..935226da8dd 100644
--- a/addons/web/static/src/js/views/graph/graph_renderer.js
+++ b/addons/web/static/src/js/views/graph/graph_renderer.js
@@ -313,7 +313,7 @@ return AbstractRenderer.extend({
                     };
                 }
                 data_dict[serie].values.push({
-                    x: tick, y: this.state.data[i].value,
+                    x: tick - 1, y: this.state.data[i].value,
                 });
                 data = _.map(data_dict, identity);
             }
diff --git a/addons/web/static/tests/views/graph_tests.js b/addons/web/static/tests/views/graph_tests.js
index 7bb2fce78b5..561b0016d28 100644
--- a/addons/web/static/tests/views/graph_tests.js
+++ b/addons/web/static/tests/views/graph_tests.js
@@ -154,6 +154,29 @@ QUnit.module('Views', {
         });
     });
 
+    QUnit.test('displaying line chart data with multiple groupbys', function (assert) {
+        // this test makes sure the line chart shows all data labels (X axis) when
+        // it is grouped by several fields
+        assert.expect(3);
+
+        var graph = createView({
+            View: GraphView,
+            model: 'foo',
+            data: this.data,
+            arch: '<graph type="line"><field name="foo" /></graph>',
+            groupBy: ['product_id', 'bar'],
+        });
+
+        assert.strictEqual(graph.$('.nv-x text:contains(xphone)').length, 1,
+            "should contain a text element with product xphone on X axis");
+        assert.strictEqual(graph.$('.nv-x text:contains(xpad)').length, 1,
+            "should contain a text element with product xpad on X axis");
+        assert.strictEqual(graph.$('text:contains(true)').length, 1,
+            "should have an entry for each value of field 'bar' in the legend");
+
+        graph.destroy();
+    });
+
     QUnit.test('switching measures', function (assert) {
         var done = assert.async();
         assert.expect(4);
diff --git a/requirements.txt b/requirements.txt
index 44b4fcb11c0..85d4a1902e7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -29,7 +29,8 @@ pyserial==3.1.1
 python-dateutil==2.5.3
 pytz==2016.7
 pyusb==1.0.0
-PyYAML==3.12
+PyYAML==3.12 ; python_version < '3.7'
+PyYAML==3.13 ; python_version >= '3.7'
 qrcode==5.3
 reportlab==3.3.0
 requests==2.11.1