diff --git a/src/widgets/styles/qstylesheetstyle.cpp b/src/widgets/styles/qstylesheetstyle.cpp
index 88c6c288e8..3f57992311 100644
--- a/src/widgets/styles/qstylesheetstyle.cpp
+++ b/src/widgets/styles/qstylesheetstyle.cpp
@@ -5035,6 +5035,14 @@ QSize QStyleSheetStyle::sizeFromContents(ContentsType ct, const QStyleOption *op
                 QRenderRule subRule = renderRule(w, opt, PseudoElement_HeaderViewSection);
                 if (subRule.hasGeometry() || subRule.hasBox() || !subRule.hasNativeBorder() || subRule.hasFont) {
                     sz = subRule.adjustSize(csz);
+                    if (!sz.isValid()) {
+                        // Try to set the missing values based on the base style.
+                        const auto baseSize = baseStyle()->sizeFromContents(ct, opt, sz, w);
+                        if (sz.width() < 0)
+                            sz.setWidth(baseSize.width());
+                        if (sz.height() < 0)
+                            sz.setHeight(baseSize.height());
+                    }
                     if (!subRule.hasGeometry()) {
                         QSize nativeContentsSize;
                         bool nullIcon = hdr->icon.isNull();
diff --git a/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp b/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
index df02815eb2..0b120985ee 100644
--- a/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
+++ b/tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp
@@ -216,6 +216,7 @@ private slots:
     void QTBUG14242_hideSectionAutoSize();
     void QTBUG50171_visualRegionForSwappedItems();
     void QTBUG53221_assertShiftHiddenRow();
+    void QTBUG75615_sizeHintWithStylesheet();
     void ensureNoIndexAtLength();
     void offsetConsistent();
 
@@ -2606,6 +2607,26 @@ void tst_QHeaderView::QTBUG53221_assertShiftHiddenRow()
     QCOMPARE(tableView.verticalHeader()->isSectionHidden(2), true);
 }
 
+void tst_QHeaderView::QTBUG75615_sizeHintWithStylesheet()
+{
+    QTableView tableView;
+    QStandardItemModel model(1, 1);
+    tableView.setModel(&model);
+    tableView.show();
+
+    const auto headerView = tableView.horizontalHeader();
+    const auto oldSizeHint = headerView->sizeHint();
+    QVERIFY(oldSizeHint.isValid());
+
+    tableView.setStyleSheet("QTableView QHeaderView::section { height: 100px;}");
+    QCOMPARE(headerView->sizeHint().width(), oldSizeHint.width());
+    QCOMPARE(headerView->sizeHint().height(), 100);
+
+    tableView.setStyleSheet("QTableView QHeaderView::section { width: 100px;}");
+    QCOMPARE(headerView->sizeHint().height(), oldSizeHint.height());
+    QCOMPARE(headerView->sizeHint().width(), 100);
+}
+
 void protected_QHeaderView::testVisualRegionForSelection()
 {
     QRegion r = visualRegionForSelection(QItemSelection(model()->index(1, 0), model()->index(1, 2)));