diff --git a/src/corelib/itemmodels/qabstractitemmodel.h b/src/corelib/itemmodels/qabstractitemmodel.h
index 7012b9fe92e..325ff1df4aa 100644
--- a/src/corelib/itemmodels/qabstractitemmodel.h
+++ b/src/corelib/itemmodels/qabstractitemmodel.h
@@ -424,7 +424,7 @@ inline QVariant QModelIndex::data(int arole) const
 inline Qt::ItemFlags QModelIndex::flags() const
 { return m ? m->flags(*this) : Qt::ItemFlags(); }
 
-inline size_t qHash(const QModelIndex &index, size_t seed) noexcept
+inline size_t qHash(const QModelIndex &index, size_t seed = 0) noexcept
 { return size_t((size_t(index.row()) << 4) + size_t(index.column()) + index.internalId()) ^ seed; }
 
 QT_END_NAMESPACE