diff --git a/src/corelib/global/qhooks.cpp b/src/corelib/global/qhooks.cpp
index 491e126b7a1..36283ec4d3f 100644
--- a/src/corelib/global/qhooks.cpp
+++ b/src/corelib/global/qhooks.cpp
@@ -67,7 +67,7 @@ quintptr Q_CORE_EXPORT qtHookData[] = {
     // The required sizes and offsets are tested in tests/auto/other/toolsupport.
     // When this fails and the change was intentional, adjust the test and
     // adjust this value here.
-    21
+    22,
 };
 
 static_assert(QHooks::LastHookIndex == sizeof(qtHookData) / sizeof(qtHookData[0]));
diff --git a/src/corelib/io/qiodevice_p.h b/src/corelib/io/qiodevice_p.h
index 83c16eeddcb..e9a8af0855c 100644
--- a/src/corelib/io/qiodevice_p.h
+++ b/src/corelib/io/qiodevice_p.h
@@ -53,9 +53,9 @@
 
 #include "QtCore/qbytearray.h"
 #include "QtCore/qiodevice.h"
-#include "QtCore/qlist.h"
 #include "QtCore/qobjectdefs.h"
 #include "QtCore/qstring.h"
+#include "QtCore/qvarlengtharray.h"
 #include "private/qringbuffer_p.h"
 #ifndef QT_NO_QOBJECT
 #include "private/qobject_p.h"
@@ -134,8 +134,8 @@ public:
     int readBufferChunkSize = QIODEVICE_BUFFERSIZE;
     int writeBufferChunkSize = 0;
 
-    QList<QRingBuffer> readBuffers;
-    QList<QRingBuffer> writeBuffers;
+    QVarLengthArray<QRingBuffer, 2> readBuffers;
+    QVarLengthArray<QRingBuffer, 1> writeBuffers;
     QString errorString;
     QIODevice::OpenMode openMode = QIODevice::NotOpen;
 
diff --git a/tests/auto/other/toolsupport/tst_toolsupport.cpp b/tests/auto/other/toolsupport/tst_toolsupport.cpp
index 7ba4286a4db..05ed44cc165 100644
--- a/tests/auto/other/toolsupport/tst_toolsupport.cpp
+++ b/tests/auto/other/toolsupport/tst_toolsupport.cpp
@@ -142,9 +142,9 @@ void tst_toolsupport::offsets_data()
 #ifdef Q_PROCESSOR_X86
         // x86 32-bit has weird alignment rules. Refer to QtPrivate::AlignOf in
         // qglobal.h for more details.
-        data << 188 << 304;
+        data << 264 << 424;
 #else
-        data << 196 << 304;
+        data << 300 << 424;
 #endif
     }
 #endif