diff --git a/src/corelib/time/qtimezone.cpp b/src/corelib/time/qtimezone.cpp
index 00d0d3a79e5..a5eaa569318 100644
--- a/src/corelib/time/qtimezone.cpp
+++ b/src/corelib/time/qtimezone.cpp
@@ -459,7 +459,6 @@ QTimeZone::QTimeZone(const QByteArray &ianaId)
             d = newBackendTimeZone();
         else // Constructor MUST produce invalid for unsupported ID.
             d = newBackendTimeZone(ianaId);
-        // else: No such ID, avoid creating a TZ cache entry for it.
     }
     // Can also handle UTC with arbitrary (valid) offset, but only do so as
     // fall-back, since either of the above may handle it more informatively.
diff --git a/src/corelib/time/qtimezoneprivate_tz.cpp b/src/corelib/time/qtimezoneprivate_tz.cpp
index f4a2df00a4b..afa7cf03700 100644
--- a/src/corelib/time/qtimezoneprivate_tz.cpp
+++ b/src/corelib/time/qtimezoneprivate_tz.cpp
@@ -998,6 +998,8 @@ QTzTimeZoneCacheEntry QTzTimeZoneCache::fetchEntry(const QByteArray &ianaId)
 // Create a named time zone
 QTzTimeZonePrivate::QTzTimeZonePrivate(const QByteArray &ianaId)
 {
+    if (!isTimeZoneIdAvailable(ianaId)) // Avoid pointlessly creating cache entries
+        return;
     static QTzTimeZoneCache tzCache;
     auto entry = tzCache.fetchEntry(ianaId);
     if (entry.m_tranTimes.isEmpty() && entry.m_posixRule.isEmpty())