diff --git a/src/widgets/dialogs/qmessagebox.cpp b/src/widgets/dialogs/qmessagebox.cpp
index 5d5b179ad85..d4deeeca138 100644
--- a/src/widgets/dialogs/qmessagebox.cpp
+++ b/src/widgets/dialogs/qmessagebox.cpp
@@ -447,20 +447,34 @@ static int oldButton(int button)
 
 int QMessageBoxPrivate::execReturnCode(QAbstractButton *button)
 {
-    int ret = buttonBox->standardButton(button);
-    if (ret == QMessageBox::NoButton) {
-        ret = customButtonList.indexOf(button); // if button == 0, correctly sets ret = -1
-    } else if (compatMode) {
-        ret = oldButton(ret);
+    if (int standardButton = buttonBox->standardButton(button)) {
+        // When using a QMessageBox with standard buttons, the return
+        // code is a StandardButton value indicating the standard button
+        // that was clicked.
+        if (compatMode)
+            return oldButton(standardButton);
+        else
+            return standardButton;
+    } else {
+        // When using QMessageBox with custom buttons, the return code
+        // is an opaque value, and the user is expected to use clickedButton()
+        // to determine which button was clicked. We make sure to keep the opaque
+        // value out of the QDialog::DialogCode range, so we can distinguish them.
+        auto customButtonIndex = customButtonList.indexOf(button);
+        if (customButtonIndex >= 0)
+            return QDialog::DialogCode::Accepted + customButtonIndex + 1;
+        else
+            return customButtonIndex; // Not found, return -1
     }
-    return ret;
 }
 
 int QMessageBoxPrivate::dialogCode() const
 {
     Q_Q(const QMessageBox);
 
-    if (clickedButton) {
+    if (rescode <= QDialog::Accepted) {
+        return rescode;
+    } else if (clickedButton) {
         switch (q->buttonRole(clickedButton)) {
         case QMessageBox::AcceptRole:
         case QMessageBox::YesRole:
diff --git a/tests/auto/widgets/dialogs/qmessagebox/tst_qmessagebox.cpp b/tests/auto/widgets/dialogs/qmessagebox/tst_qmessagebox.cpp
index b85a89415e9..94afff6e408 100644
--- a/tests/auto/widgets/dialogs/qmessagebox/tst_qmessagebox.cpp
+++ b/tests/auto/widgets/dialogs/qmessagebox/tst_qmessagebox.cpp
@@ -62,6 +62,8 @@ private slots:
 
     void hideNativeByDestruction();
 
+    void explicitDoneAfterButtonClicked();
+
     void cleanup();
 };
 
@@ -437,7 +439,7 @@ void tst_QMessageBox::shortcut()
     msgBox.addButton("&Maybe", QMessageBox::YesRole);
     ExecCloseHelper closeHelper;
     closeHelper.start(Qt::Key_M, &msgBox);
-    QCOMPARE(msgBox.exec(), 2);
+    QCOMPARE(msgBox.exec(), 4);
 }
 #endif
 
@@ -509,7 +511,7 @@ QT_WARNING_DISABLE_DEPRECATED
     // the button text versions
     closeHelper.start(Qt::Key_Enter);
     ret = QMessageBox::information(nullptr, "title", "text", "Yes", "No", QString(), 1);
-    COMPARE(ret, 1);
+    COMPARE(ret, 3); // Custom button opaque result
     QVERIFY(closeHelper.done());
 #endif // QT_DEPRECATED_SINCE(6, 2)
 #undef COMPARE
@@ -538,9 +540,9 @@ void tst_QMessageBox::instanceSourceCompat()
 #ifndef Q_OS_MAC
     // mnemonics are not used on OS X
     closeHelper.start(QKeyCombination(Qt::ALT | Qt::Key_R).toCombined(), &mb);
-    QCOMPARE(mb.exec(), 0);
+    QCOMPARE(mb.exec(), 2);
     closeHelper.start(QKeyCombination(Qt::ALT | Qt::Key_Z).toCombined(), &mb);
-    QCOMPARE(mb.exec(), 1);
+    QCOMPARE(mb.exec(), 3);
 #endif
 }
 
@@ -815,5 +817,51 @@ void tst_QMessageBox::hideNativeByDestruction()
     QVERIFY(QTest::qWaitFor(windowActive));
 }
 
+void tst_QMessageBox::explicitDoneAfterButtonClicked()
+{
+    QMessageBox msgBox;
+    auto *standardButton = msgBox.addButton(QMessageBox::Ok);
+    auto *customButton = msgBox.addButton("Custom", QMessageBox::RejectRole);
+
+    QSignalSpy acceptedSpy(&msgBox, &QDialog::accepted);
+    QSignalSpy rejectedSpy(&msgBox, &QDialog::rejected);
+
+    msgBox.setDefaultButton(standardButton);
+    ExecCloseHelper closeHelper;
+    closeHelper.start(Qt::Key_Enter, &msgBox);
+    msgBox.exec();
+    QCOMPARE(msgBox.clickedButton(), standardButton);
+    QCOMPARE(msgBox.result(), QMessageBox::Ok);
+    QCOMPARE(acceptedSpy.size(), 1);
+    QCOMPARE(rejectedSpy.size(), 0);
+
+    msgBox.accept();
+    QCOMPARE(msgBox.result(), QDialog::Accepted);
+    QCOMPARE(acceptedSpy.size(), 2);
+    QCOMPARE(rejectedSpy.size(), 0);
+    msgBox.reject();
+    QCOMPARE(msgBox.result(), QDialog::Rejected);
+    QCOMPARE(acceptedSpy.size(), 2);
+    QCOMPARE(rejectedSpy.size(), 1);
+
+    msgBox.setDefaultButton(customButton);
+    closeHelper.start(Qt::Key_Enter, &msgBox);
+    msgBox.exec();
+    QCOMPARE(msgBox.clickedButton(), customButton);
+    QVERIFY(msgBox.result() != QDialog::Accepted);
+    QVERIFY(msgBox.result() != QDialog::Rejected);
+    QCOMPARE(acceptedSpy.size(), 2);
+    QCOMPARE(rejectedSpy.size(), 2);
+
+    msgBox.accept();
+    QCOMPARE(msgBox.result(), QDialog::Accepted);
+    QCOMPARE(acceptedSpy.size(), 3);
+    QCOMPARE(rejectedSpy.size(), 2);
+    msgBox.reject();
+    QCOMPARE(msgBox.result(), QDialog::Rejected);
+    QCOMPARE(acceptedSpy.size(), 3);
+    QCOMPARE(rejectedSpy.size(), 3);
+}
+
 QTEST_MAIN(tst_QMessageBox)
 #include "tst_qmessagebox.moc"