diff --git a/src/corelib/io/qurlidna.cpp b/src/corelib/io/qurlidna.cpp
index 16bb924b17..8dd01e0723 100644
--- a/src/corelib/io/qurlidna.cpp
+++ b/src/corelib/io/qurlidna.cpp
@@ -2422,8 +2422,8 @@ static bool qt_is_idn_enabled(const QString &domain)
         return false;
 
     int len = domain.size() - idx - 1;
-    QString tldString(domain.constData() + idx + 1, len);
-    qt_nameprep(&tldString, 0);
+    QString tldString = qt_ACE_do(QString::fromRawData(domain.constData() + idx + 1, len), ToAceOnly, ForbidLeadingDot);
+    len = tldString.size();
 
     const QChar *tld = tldString.constData();
 
diff --git a/tests/auto/corelib/io/qurlinternal/tst_qurlinternal.cpp b/tests/auto/corelib/io/qurlinternal/tst_qurlinternal.cpp
index f5835ec5f4..766338e4f8 100644
--- a/tests/auto/corelib/io/qurlinternal/tst_qurlinternal.cpp
+++ b/tests/auto/corelib/io/qurlinternal/tst_qurlinternal.cpp
@@ -670,6 +670,14 @@ void tst_QUrlInternal::ace_testsuite()
         QCOMPARE(QUrl::fromAce(domain.toLatin1()), fromace + suffix);
     QCOMPARE(QUrl::fromAce(QUrl::toAce(domain)), unicode + suffix);
 
+    QUrl u;
+    u.setHost(domain);
+    QVERIFY(u.isValid());
+    QCOMPARE(u.host(), unicode + suffix);
+    QCOMPARE(u.host(QUrl::EncodeUnicode), toace + suffix);
+    QCOMPARE(u.toEncoded(), "//" + toace.toLatin1() + suffix);
+    QCOMPARE(u.toDisplayString(), "//" + unicode + suffix);
+
     domain = in + (suffix ? ".troll.No" : "");
     QCOMPARE(QString::fromLatin1(QUrl::toAce(domain)), toace + suffix);
     if (fromace != ".")