diff --git a/src/private/pack_p.cpp b/src/private/pack_p.cpp
index 9419567..d751bde 100644
--- a/src/private/pack_p.cpp
+++ b/src/private/pack_p.cpp
@@ -20,7 +20,11 @@ QReadWriteLock MsgPackPrivate::packers_lock;
 quint8 *MsgPackPrivate::pack(const QVariant &v, quint8 *p, bool wr, QVector<QByteArray> &user_data)
 {
     QMetaType::Type t = (QMetaType::Type)v.type();
-    if ((v.isNull() && !v.isValid()) || t == 51) // QMetaType::Nullptr
+#if QT_VERSION > QT_VERSION_CHECK(5, 8, 0)
+    if ((v.isNull() && !v.isValid()) || t == QMetaType::Nullptr)
+#else
+    if (v.isNull() && !v.isValid())
+#endif  
         p = pack_nil(p, wr);
     else if (t == QMetaType::Int)
         p = pack_int(v.toInt(), p, wr);
diff --git a/tests/pack/pack_test.cpp b/tests/pack/pack_test.cpp
index e25e3f7..263389f 100644
--- a/tests/pack/pack_test.cpp
+++ b/tests/pack/pack_test.cpp
@@ -27,12 +27,19 @@ private Q_SLOTS:
 void PackTest::test_nil()
 {
     QVariant v;
-    v.setValue(nullptr);
-    QVERIFY((QMetaType::Type)v.type() == 51); // QMetaType::Nullptr
     QByteArray arr = MsgPack::pack(v);
     quint8 *p = (quint8 *)arr.data();
     QVERIFY(arr.size() == 1);
     QVERIFY(p[0] == 0xc0);
+
+#if QT_VERSION > QT_VERSION_CHECK(5, 8, 0)
+    v.setValue(nullptr);
+    QVERIFY((QMetaType::Type)v.type() == QMetaType::Nullptr);
+    arr = MsgPack::pack(v);
+    p = (quint8 *)arr.data();
+    QVERIFY(arr.size() == 1);
+    QVERIFY(p[0] == 0xc0);
+#endif
 }
 
 void PackTest::test_bool()