diff --git a/src/widgets/util/qcompleter.cpp b/src/widgets/util/qcompleter.cpp
index 64b7b12e90..18c8ed2bd2 100644
--- a/src/widgets/util/qcompleter.cpp
+++ b/src/widgets/util/qcompleter.cpp
@@ -829,6 +829,7 @@ void QCompleterPrivate::_q_complete(QModelIndex index, bool highlighted)
 
     if (!index.isValid() || (!proxy->showAll && (index.row() >= proxy->engine->matchCount()))) {
         completion = prefix;
+        index = QModelIndex();
     } else {
         if (!(index.flags() & Qt::ItemIsEnabled))
             return;
diff --git a/tests/auto/widgets/util/qcompleter/tst_qcompleter.cpp b/tests/auto/widgets/util/qcompleter/tst_qcompleter.cpp
index 0f7993540c..3a6fca7146 100644
--- a/tests/auto/widgets/util/qcompleter/tst_qcompleter.cpp
+++ b/tests/auto/widgets/util/qcompleter/tst_qcompleter.cpp
@@ -1305,10 +1305,15 @@ void tst_QCompleter::task246056_setCompletionPrefix()
     comboBox.show();
     QApplication::setActiveWindow(&comboBox);
     QVERIFY(QTest::qWaitForWindowActive(&comboBox));
+    QSignalSpy spy(comboBox.completer(), SIGNAL(activated(QModelIndex)));
     QTest::keyPress(&comboBox, 'a');
     QTest::keyPress(comboBox.completer()->popup(), Qt::Key_Down);
     QTest::keyPress(comboBox.completer()->popup(), Qt::Key_Down);
     QTest::keyPress(comboBox.completer()->popup(), Qt::Key_Enter); // don't crash!
+    QCOMPARE(spy.count(), 1);
+    QList<QVariant> arguments = spy.at(0);
+    QModelIndex index = arguments.at(0).value<QModelIndex>();
+    QVERIFY(!index.isValid());
 }
 
 class task250064_TextEdit : public QTextEdit