diff --git a/src/gui/image/qpixmapcache.cpp b/src/gui/image/qpixmapcache.cpp
index 016cd1a9873..82b7060d6f0 100644
--- a/src/gui/image/qpixmapcache.cpp
+++ b/src/gui/image/qpixmapcache.cpp
@@ -439,6 +439,7 @@ void QPMCache::clear()
         killTimer(theid);
         theid = 0;
     }
+    cacheKeys.clear();
 }
 
 QPixmapCache::KeyData* QPMCache::getKeyData(QPixmapCache::Key *key)
diff --git a/tests/auto/gui/image/qpixmapcache/tst_qpixmapcache.cpp b/tests/auto/gui/image/qpixmapcache/tst_qpixmapcache.cpp
index d4c39a2130b..de785fd160d 100644
--- a/tests/auto/gui/image/qpixmapcache/tst_qpixmapcache.cpp
+++ b/tests/auto/gui/image/qpixmapcache/tst_qpixmapcache.cpp
@@ -13,6 +13,8 @@ Q_AUTOTEST_EXPORT int qt_qpixmapcache_qpixmapcache_total_used();
 Q_AUTOTEST_EXPORT int q_QPixmapCache_keyHashSize();
 QT_END_NAMESPACE
 
+using namespace Qt::StringLiterals;
+
 class tst_QPixmapCache : public QObject
 {
     Q_OBJECT
@@ -34,6 +36,7 @@ private slots:
     void clear();
     void pixmapKey();
     void noLeak();
+    void clearDoesNotLeakStringKeys();
     void strictCacheLimit();
     void noCrashOnLargeInsert();
 };
@@ -478,6 +481,39 @@ void tst_QPixmapCache::noLeak()
     QCOMPARE(oldSize, newSize);
 }
 
+void tst_QPixmapCache::clearDoesNotLeakStringKeys()
+{
+    QPixmapCache::setCacheLimit(20); // 20KiB
+    //
+    // GIVEN: a QPixmap with QString key `key` in QPixmapCache
+    //
+    QString key;
+    {
+        QPixmap pm(64, 64);
+        QCOMPARE_LT(pm.width() * pm.height() * std::ceil(pm.depth() / 8.0),
+                    QPixmapCache::cacheLimit() * 1024);
+        pm.fill(Qt::transparent);
+        key = u"theKey"_s.repeated(20); // avoid eventual QString SSO
+        QVERIFY(key.isDetached());
+        QPixmapCache::insert(key, pm);
+    }
+    QVERIFY(!key.isDetached()); // was saved inside QPixmapCache
+
+    //
+    // WHEN: clearing the cache:
+    //
+    QPixmapCache::clear();
+
+    //
+    // THEN: `key` is no longer referenced by QPixmapCache:
+    //
+    QVERIFY(key.isDetached());
+    // verify that the pixmap is really gone from the cache
+    // (do it after the key check, because QPixmapCache cleans up `key` on a failed lookup)
+    QPixmap r;
+    QVERIFY(!QPixmapCache::find(key, &r));
+}
+
 
 void tst_QPixmapCache::strictCacheLimit()
 {