diff --git a/src/corelib/tools/qdatetime.cpp b/src/corelib/tools/qdatetime.cpp
index a642358770..bf92be2dd4 100644
--- a/src/corelib/tools/qdatetime.cpp
+++ b/src/corelib/tools/qdatetime.cpp
@@ -2842,6 +2842,9 @@ inline bool QDateTime::Data::isShort() const
 {
     bool b = quintptr(d) & QDateTimePrivate::ShortData;
 
+    // sanity check:
+    Q_ASSERT(b || (d->m_status & QDateTimePrivate::ShortData) == 0);
+
     // even if CanBeSmall = false, we have short data for a default-constructed
     // QDateTime object. But it's unlikely.
     if (CanBeSmall)
@@ -3658,7 +3661,7 @@ void QDateTime::setMSecsSinceEpoch(qint64 msecs)
         d.data.status = status;
     } else {
         d.detach();
-        d->m_status = status;
+        d->m_status = status & ~QDateTimePrivate::ShortData;
         d->m_msecs = msecs;
     }
 
diff --git a/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp b/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp
index e54edb490c..33844feafe 100644
--- a/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp
+++ b/tests/auto/corelib/tools/qdatetime/tst_qdatetime.cpp
@@ -667,6 +667,29 @@ void tst_QDateTime::setMSecsSinceEpoch()
     QCOMPARE(dt.time(), utc.time());
     QCOMPARE(dt.timeSpec(), Qt::UTC);
 
+    {
+        QDateTime dt1 = QDateTime::fromMSecsSinceEpoch(msecs, Qt::UTC);
+        QCOMPARE(dt1, utc);
+        QCOMPARE(dt1.date(), utc.date());
+        QCOMPARE(dt1.time(), utc.time());
+        QCOMPARE(dt1.timeSpec(), Qt::UTC);
+    }
+    {
+        QDateTime dt1(utc.date(), utc.time(), Qt::UTC);
+        QCOMPARE(dt1, utc);
+        QCOMPARE(dt1.date(), utc.date());
+        QCOMPARE(dt1.time(), utc.time());
+        QCOMPARE(dt1.timeSpec(), Qt::UTC);
+    }
+    {
+        // used to fail to clear the ShortData bit, causing corruption
+        QDateTime dt1 = dt.addDays(0);
+        QCOMPARE(dt1, utc);
+        QCOMPARE(dt1.date(), utc.date());
+        QCOMPARE(dt1.time(), utc.time());
+        QCOMPARE(dt1.timeSpec(), Qt::UTC);
+    }
+
     if (zoneIsCET) {
         QCOMPARE(dt.toLocalTime(), cet);