diff --git a/src/corelib/time/qtimezoneprivate_mac.mm b/src/corelib/time/qtimezoneprivate_mac.mm
index b051b08ec7c..8d975467301 100644
--- a/src/corelib/time/qtimezoneprivate_mac.mm
+++ b/src/corelib/time/qtimezoneprivate_mac.mm
@@ -56,12 +56,10 @@ QMacTimeZonePrivate *QMacTimeZonePrivate::clone() const
 
 void QMacTimeZonePrivate::init(const QByteArray &ianaId)
 {
-    if (availableTimeZoneIds().contains(ianaId)) {
-        m_nstz = [[NSTimeZone timeZoneWithName:QString::fromUtf8(ianaId).toNSString()] retain];
-        if (m_nstz)
-            m_id = ianaId;
-    }
-    if (!m_nstz) {
+    m_nstz = [[NSTimeZone timeZoneWithName:QString::fromUtf8(ianaId).toNSString()] retain];
+    if (m_nstz) {
+        m_id = ianaId;
+    } else {
         // macOS has been seen returning a systemTimeZone which reports its name
         // as Asia/Kolkata, which doesn't appear in knownTimeZoneNames (which
         // calls the zone Asia/Calcutta). So explicitly check for the name
@@ -285,6 +283,12 @@ QByteArray QMacTimeZonePrivate::systemTimeZoneId() const
     return QString::fromNSString(NSTimeZone.systemTimeZone.name).toUtf8();
 }
 
+bool QMacTimeZonePrivate::isTimeZoneIdAvailable(const QByteArray& ianaId) const
+{
+    QMacAutoReleasePool pool;
+    return [NSTimeZone timeZoneWithName:QString::fromUtf8(ianaId).toNSString()] != nil;
+}
+
 QList<QByteArray> QMacTimeZonePrivate::availableTimeZoneIds() const
 {
     NSEnumerator *enumerator = NSTimeZone.knownTimeZoneNames.objectEnumerator;
diff --git a/src/corelib/time/qtimezoneprivate_p.h b/src/corelib/time/qtimezoneprivate_p.h
index 72b45e851bf..43a24449887 100644
--- a/src/corelib/time/qtimezoneprivate_p.h
+++ b/src/corelib/time/qtimezoneprivate_p.h
@@ -367,7 +367,7 @@ public:
     Data previousTransition(qint64 beforeMSecsSinceEpoch) const override;
 
     QByteArray systemTimeZoneId() const override;
-
+    bool isTimeZoneIdAvailable(const QByteArray &ianaId) const override;
     QList<QByteArray> availableTimeZoneIds() const override;
 
     NSTimeZone *nsTimeZone() const;