5 files changed, 14 insertions, 11 deletions
diff --git a/src/corelib/io/qabstractfileengine.cpp b/src/corelib/io/qabstractfileengine.cpp
index 70e68be21c1..a3fa9c00f86 100644
--- a/src/corelib/io/qabstractfileengine.cpp
+++ b/src/corelib/io/qabstractfileengine.cpp
@@ -318,9 +318,8 @@ std::unique_ptr<QAbstractFileEngine> QAbstractFileEngine::create(const QString &
 
    \sa setFileName()
  */
-QAbstractFileEngine::QAbstractFileEngine() : d_ptr(new QAbstractFileEnginePrivate)
+QAbstractFileEngine::QAbstractFileEngine() : d_ptr(new QAbstractFileEnginePrivate(this))
 {
-    d_ptr->q_ptr = this;
 }
 
 /*!
@@ -330,7 +329,7 @@ QAbstractFileEngine::QAbstractFileEngine() : d_ptr(new QAbstractFileEnginePrivat
  */
 QAbstractFileEngine::QAbstractFileEngine(QAbstractFileEnginePrivate &dd) : d_ptr(&dd)
 {
-    d_ptr->q_ptr = this;
+    Q_ASSERT(d_ptr->q_ptr == this);
 }
 
 /*!
diff --git a/src/corelib/io/qabstractfileengine_p.h b/src/corelib/io/qabstractfileengine_p.h
index 5e6232af71a..704b0c94c55 100644
--- a/src/corelib/io/qabstractfileengine_p.h
+++ b/src/corelib/io/qabstractfileengine_p.h
@@ -242,8 +242,8 @@ private:
 class QAbstractFileEnginePrivate
 {
 public:
-    inline QAbstractFileEnginePrivate()
-        : fileError(QFile::UnspecifiedError)
+    inline QAbstractFileEnginePrivate(QAbstractFileEngine *q)
+        : fileError(QFile::UnspecifiedError), q_ptr(q)
     {
     }
     inline virtual ~QAbstractFileEnginePrivate() { }
@@ -251,7 +251,7 @@ public:
     QFile::FileError fileError;
     QString errorString;
 
-    QAbstractFileEngine *q_ptr;
+    QAbstractFileEngine *const q_ptr;
     Q_DECLARE_PUBLIC(QAbstractFileEngine)
 };
 
diff --git a/src/corelib/io/qfsfileengine.cpp b/src/corelib/io/qfsfileengine.cpp
index 2f9087bf6a3..6610b6ecd66 100644
--- a/src/corelib/io/qfsfileengine.cpp
+++ b/src/corelib/io/qfsfileengine.cpp
@@ -76,7 +76,8 @@ static_assert(sizeof(SignedIOType) == sizeof(UnsignedIOType),
 */
 
 //**************** QFSFileEnginePrivate
-QFSFileEnginePrivate::QFSFileEnginePrivate() : QAbstractFileEnginePrivate()
+QFSFileEnginePrivate::QFSFileEnginePrivate(QAbstractFileEngine *q)
+    : QAbstractFileEnginePrivate(q)
 {
     init();
 }
@@ -108,7 +109,7 @@ void QFSFileEnginePrivate::init()
     Constructs a QFSFileEngine for the file name \a file.
 */
 QFSFileEngine::QFSFileEngine(const QString &file)
-    : QAbstractFileEngine(*new QFSFileEnginePrivate)
+    : QAbstractFileEngine(*new QFSFileEnginePrivate(this))
 {
     Q_D(QFSFileEngine);
     d->fileEntry = QFileSystemEntry(file);
@@ -117,7 +118,7 @@ QFSFileEngine::QFSFileEngine(const QString &file)
 /*!
     Constructs a QFSFileEngine.
 */
-QFSFileEngine::QFSFileEngine() : QAbstractFileEngine(*new QFSFileEnginePrivate)
+QFSFileEngine::QFSFileEngine() : QAbstractFileEngine(*new QFSFileEnginePrivate(this))
 {
 }
 
diff --git a/src/corelib/io/qfsfileengine_p.h b/src/corelib/io/qfsfileengine_p.h
index 5e77804606a..f6b3a39e647 100644
--- a/src/corelib/io/qfsfileengine_p.h
+++ b/src/corelib/io/qfsfileengine_p.h
@@ -222,7 +222,7 @@ public:
         return (openMode & QFile::WriteOnly) && !(openMode & QFile::ExistingOnly);
     }
 protected:
-    QFSFileEnginePrivate();
+    QFSFileEnginePrivate(QAbstractFileEngine *q);
 
     void init();
 
diff --git a/src/corelib/io/qresource.cpp b/src/corelib/io/qresource.cpp
index 83df4e1aec1..bd208896861 100644
--- a/src/corelib/io/qresource.cpp
+++ b/src/corelib/io/qresource.cpp
@@ -1397,6 +1397,9 @@ private:
     // minimum size for which we'll try to re-open ourselves in mapUncompressed()
     static constexpr qsizetype RemapCompressedThreshold = 16384;
 protected:
+    QResourceFileEnginePrivate(QAbstractFileEngine *q) :
+        QAbstractFileEnginePrivate(q) {}
+
     ~QResourceFileEnginePrivate()
     {
         if (mustUnmap)
@@ -1410,7 +1413,7 @@ bool QResourceFileEngine::caseSensitive() const
 }
 
 QResourceFileEngine::QResourceFileEngine(const QString &file) :
-    QAbstractFileEngine(*new QResourceFileEnginePrivate)
+    QAbstractFileEngine(*new QResourceFileEnginePrivate(this))
 {
     Q_D(QResourceFileEngine);
     d->resource.setFileName(file);