4 files changed, 39 insertions, 10 deletions
diff --git a/src/qml/qml/qqmlbinding_p.h b/src/qml/qml/qqmlbinding_p.h
index 08e61a7aef..00aa0d6f58 100644
--- a/src/qml/qml/qqmlbinding_p.h
+++ b/src/qml/qml/qqmlbinding_p.h
@@ -79,6 +79,10 @@ public:
     };
 
     QVariant evaluate();
+    bool evaluate(void *result, QMetaType type)
+    {
+        return QQmlJavaScriptExpression::evaluate(&result, &type, 0);
+    }
 
     void expressionChanged() override;
 
@@ -116,10 +120,6 @@ protected:
                    QQmlPropertyData::WriteFlags flags);
 
     QV4::ReturnedValue evaluate(bool *isUndefined);
-    bool evaluate(void *result, QMetaType type)
-    {
-        return QQmlJavaScriptExpression::evaluate(&result, &type, 0);
-    }
 
 private:
     static QQmlBinding *newBinding(const QQmlPropertyData *property);
diff --git a/src/quick/util/qquickstategroup.cpp b/src/quick/util/qquickstategroup.cpp
index 68caa6590d..b4be946dc3 100644
--- a/src/quick/util/qquickstategroup.cpp
+++ b/src/quick/util/qquickstategroup.cpp
@@ -353,11 +353,10 @@ bool QQuickStateGroupPrivate::updateAutoState()
                 if (abstractBinding && abstractBinding->kind() == QQmlAbstractBinding::QmlBinding) {
                     QQmlBinding *binding = static_cast<QQmlBinding *>(abstractBinding);
                     if (binding->hasValidContext()) {
-                        QVariant evalResult = binding->evaluate();
-                        if (evalResult.metaType() == QMetaType::fromType<QJSValue>())
-                            whenValue = evalResult.value<QJSValue>().toBool();
-                        else
-                            whenValue = evalResult.toBool();
+                        const auto boolType = QMetaType::fromType<bool>();
+                        const bool isUndefined = !binding->evaluate(&whenValue, boolType);
+                        if (isUndefined)
+                            whenValue = false;
                     }
                 }
 
diff --git a/tests/auto/quick/qquickstates/data/jsValueWhen2.qml b/tests/auto/quick/qquickstates/data/jsValueWhen2.qml
new file mode 100644
index 0000000000..e1f173138e
--- /dev/null
+++ b/tests/auto/quick/qquickstates/data/jsValueWhen2.qml
@@ -0,0 +1,20 @@
+import QtQuick 2.15
+
+Item {
+    id: root
+    property var prop: null
+    property bool works: false
+    states: [
+        State {
+            name: "mystate"
+            when: root.prop
+            PropertyChanges {
+                target: root
+                works: "works"
+            }
+        }
+    ]
+    Component.onCompleted: root.prop = Qt.createQmlObject(
+        "import QtQml 2.15\nQtObject {}",
+        root, "dynamicSnippet")
+}
diff --git a/tests/auto/quick/qquickstates/tst_qquickstates.cpp b/tests/auto/quick/qquickstates/tst_qquickstates.cpp
index 62fca7d280..44187d2b65 100644
--- a/tests/auto/quick/qquickstates/tst_qquickstates.cpp
+++ b/tests/auto/quick/qquickstates/tst_qquickstates.cpp
@@ -175,6 +175,7 @@ private slots:
     void revertListMemoryLeak();
     void duplicateStateName();
     void trivialWhen();
+    void jsValueWhen_data();
     void jsValueWhen();
     void noStateOsciallation();
     void parentChangeCorrectReversal();
@@ -1695,11 +1696,20 @@ void tst_qquickstates::trivialWhen()
     QVERIFY(root);
 }
 
+
+void tst_qquickstates::jsValueWhen_data()
+{
+    QTest::addColumn<QByteArray>("fileName");
+    QTest::addRow("jsObject") << QByteArray("jsValueWhen.qml");
+    QTest::addRow("qmlObject") << QByteArray("jsValueWhen2.qml");
+}
+
 void tst_qquickstates::jsValueWhen()
 {
+    QFETCH(QByteArray, fileName);
     QQmlEngine engine;
 
-    QQmlComponent c(&engine, testFileUrl("jsValueWhen.qml"));
+    QQmlComponent c(&engine, testFileUrl(fileName.constData()));
     QScopedPointer<QObject> root(c.create());
     QVERIFY(root);
     QVERIFY(root->property("works").toBool());