diff --git a/src/widgets/kernel/qboxlayout.cpp b/src/widgets/kernel/qboxlayout.cpp
index 501883e85a9..00860f14ebc 100644
--- a/src/widgets/kernel/qboxlayout.cpp
+++ b/src/widgets/kernel/qboxlayout.cpp
@@ -413,8 +413,9 @@ int QBoxLayoutPrivate::validateIndex(int index) const
     if (index < 0)
         return list.size(); // append
 
-    Q_ASSERT_X(index >= 0 && index <= list.size(), "QBoxLayout::insert", "index out of range");
-    return index;
+    if (index > list.size())
+        qWarning("QBoxLayout::insert: index %d out of range (max: %d)", index, int(list.size()));
+    return index <= list.size() ? index : list.size();
 }
 
 /*!
@@ -811,8 +812,10 @@ void QBoxLayout::addItem(QLayoutItem *item)
 }
 
 /*!
-    Inserts \a item into this box layout at position \a index. If \a
-    index is negative, the item is added at the end.
+    Inserts \a item into this box layout at position \a index.
+    Index must be either negative or within the range 0 to count(),
+    inclusive. If \a index is negative or count(), the item is
+    added at the end.
 
     \sa addItem(), insertWidget(), insertLayout(), insertStretch(),
         insertSpacing()
diff --git a/tests/auto/widgets/kernel/qboxlayout/tst_qboxlayout.cpp b/tests/auto/widgets/kernel/qboxlayout/tst_qboxlayout.cpp
index a9122d634e3..91902b5fee0 100644
--- a/tests/auto/widgets/kernel/qboxlayout/tst_qboxlayout.cpp
+++ b/tests/auto/widgets/kernel/qboxlayout/tst_qboxlayout.cpp
@@ -42,6 +42,7 @@ private slots:
     void taskQTBUG_40609_addingLayoutToItself();
     void replaceWidget();
     void indexOf();
+    void invalidIndex();
 };
 
 class CustomLayoutStyle : public QProxyStyle
@@ -584,5 +585,14 @@ void tst_QBoxLayout::indexOf()
     QCOMPARE(inner->indexOf(inner->itemAt(0)), 0);
 }
 
+void tst_QBoxLayout::invalidIndex()
+{
+    QLabel lbl("aaa");
+    QVBoxLayout layout;
+    layout.insertWidget(1, &lbl);    // should not crash
+    QVERIFY(layout.itemAt(0));
+    QCOMPARE(layout.itemAt(0)->widget(), &lbl);
+}
+
 QTEST_MAIN(tst_QBoxLayout)
 #include "tst_qboxlayout.moc"