diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index f93b60d4bbd..80a8d1eec9f 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -521,7 +521,9 @@ void QList<T>::reserve(qsizetype asize)
 template <typename T>
 inline void QList<T>::squeeze()
 {
-    if (d->needsDetach() || size() != capacity()) {
+    if (!d.isMutable())
+        return;
+    if (d->needsDetach() || size() < capacity()) {
         // must allocate memory
         DataPointer detached(Data::allocate(size(), d->detachFlags() & ~Data::CapacityReserved));
         if (size()) {
diff --git a/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp b/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp
index 27d4fd87d6c..288bc6e120a 100644
--- a/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp
+++ b/tests/auto/corelib/tools/qarraydata/tst_qarraydata.cpp
@@ -1870,6 +1870,8 @@ void tst_QArrayData::literals()
         QCOMPARE(l.capacity(), 0);
         for (int i = 0; i < 3; ++i)
             QCOMPARE(l.at(i).value, i);
+        l.squeeze(); // shouldn't detach
+        QCOMPARE(l.capacity(), 0);
 
         (void)l.begin(); // "detach"
 
diff --git a/tests/auto/corelib/tools/qlist/tst_qlist.cpp b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
index 8a7100d14c1..d1e321f4dbe 100644
--- a/tests/auto/corelib/tools/qlist/tst_qlist.cpp
+++ b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
@@ -3076,6 +3076,9 @@ void tst_QList::fromReadOnlyData() const
 {
     {
         QVector<char> d = QVector<char>::fromReadOnlyData("ABCDEFGHIJ");
+        QCOMPARE(d.capacity(), 0);
+        d.squeeze();
+        QCOMPARE(d.capacity(), 0);
         QCOMPARE(d.size(), 10u + 1u);
         for (int i = 0; i < 10; ++i)
             QCOMPARE(d.data()[i], char('A' + i));