diff --git a/qmake/library/qmakeparser.cpp b/qmake/library/qmakeparser.cpp
index 131ec6db6ac..4c8360b4598 100644
--- a/qmake/library/qmakeparser.cpp
+++ b/qmake/library/qmakeparser.cpp
@@ -45,11 +45,17 @@ QT_BEGIN_NAMESPACE
 //
 ///////////////////////////////////////////////////////////////////////
 
+ProFileCache::ProFileCache()
+{
+    QMakeVfs::ref();
+}
+
 ProFileCache::~ProFileCache()
 {
     for (const Entry &ent : qAsConst(parsed_files))
         if (ent.pro)
             ent.pro->deref();
+    QMakeVfs::deref();
 }
 
 void ProFileCache::discardFile(const QString &fileName, QMakeVfs *vfs)
diff --git a/qmake/library/qmakeparser.h b/qmake/library/qmakeparser.h
index e9529f8bf68..7b96d4e88f8 100644
--- a/qmake/library/qmakeparser.h
+++ b/qmake/library/qmakeparser.h
@@ -201,7 +201,7 @@ Q_DECLARE_OPERATORS_FOR_FLAGS(QMakeParser::ParseFlags)
 class QMAKE_EXPORT ProFileCache
 {
 public:
-    ProFileCache() {}
+    ProFileCache();
     ~ProFileCache();
 
     void discardFile(int id);
diff --git a/qmake/library/qmakevfs.cpp b/qmake/library/qmakevfs.cpp
index 2239a2beec6..3a54ef40235 100644
--- a/qmake/library/qmakevfs.cpp
+++ b/qmake/library/qmakevfs.cpp
@@ -52,11 +52,38 @@ QMakeVfs::QMakeVfs()
 #ifndef QT_NO_TEXTCODEC
     m_textCodec = 0;
 #endif
+    ref();
+}
+
+QMakeVfs::~QMakeVfs()
+{
+    deref();
+}
+
+void QMakeVfs::ref()
+{
+#ifdef PROEVALUATOR_THREAD_SAFE
+    QMutexLocker locker(&s_mutex);
+#endif
+    ++s_refCount;
+}
+
+void QMakeVfs::deref()
+{
+#ifdef PROEVALUATOR_THREAD_SAFE
+    QMutexLocker locker(&s_mutex);
+#endif
+    if (!--s_refCount) {
+        s_fileIdCounter = 0;
+        s_fileIdMap.clear();
+        s_idFileMap.clear();
+    }
 }
 
 #ifdef PROPARSER_THREAD_SAFE
 QMutex QMakeVfs::s_mutex;
 #endif
+int QMakeVfs::s_refCount;
 QAtomicInt QMakeVfs::s_fileIdCounter;
 QHash<QString, int> QMakeVfs::s_fileIdMap;
 QHash<int, QString> QMakeVfs::s_idFileMap;
@@ -114,16 +141,6 @@ QString QMakeVfs::fileNameForId(int id)
     return s_idFileMap.value(id);
 }
 
-void QMakeVfs::clearIds()
-{
-#ifdef PROEVALUATOR_THREAD_SAFE
-    QMutexLocker locker(&s_mutex);
-#endif
-    s_fileIdCounter = 0;
-    s_fileIdMap.clear();
-    s_idFileMap.clear();
-}
-
 bool QMakeVfs::writeFile(int id, QIODevice::OpenMode mode, VfsFlags flags,
                          const QString &contents, QString *errStr)
 {
diff --git a/qmake/library/qmakevfs.h b/qmake/library/qmakevfs.h
index 12172254714..68c21a3d373 100644
--- a/qmake/library/qmakevfs.h
+++ b/qmake/library/qmakevfs.h
@@ -76,10 +76,13 @@ public:
     Q_DECLARE_FLAGS(VfsFlags, VfsFlag)
 
     QMakeVfs();
+    ~QMakeVfs();
+
+    static void ref();
+    static void deref();
 
     int idForFileName(const QString &fn, VfsFlags flags);
     QString fileNameForId(int id);
-    static void clearIds();
     bool writeFile(int id, QIODevice::OpenMode mode, VfsFlags flags, const QString &contents, QString *errStr);
     ReadResult readFile(int id, QString *contents, QString *errStr);
     bool exists(const QString &fn, QMakeVfs::VfsFlags flags);
@@ -97,6 +100,7 @@ private:
 #ifdef PROEVALUATOR_THREAD_SAFE
     static QMutex s_mutex;
 #endif
+    static int s_refCount;
     static QAtomicInt s_fileIdCounter;
     // Qt Creator's ProFile cache is a singleton to maximize its cross-project
     // effectiveness (shared prf files from QtVersions).