diff --git a/src/plugins/qtsupport/profilereader.cpp b/src/plugins/qtsupport/profilereader.cpp
index 86ec0f16d7f..15eb960071c 100644
--- a/src/plugins/qtsupport/profilereader.cpp
+++ b/src/plugins/qtsupport/profilereader.cpp
@@ -166,7 +166,6 @@ void ProFileCacheManager::clear()
     // loop is concerned. Use a shared pointer once this is not true anymore.
     delete m_cache;
     m_cache = 0;
-    QMakeVfs::clearIds();
 }
 
 void ProFileCacheManager::discardFiles(const QString &prefix, QMakeVfs *vfs)
diff --git a/src/shared/proparser/qmakevfs.cpp b/src/shared/proparser/qmakevfs.cpp
index d7248fbd5be..c5c5b75c749 100644
--- a/src/shared/proparser/qmakevfs.cpp
+++ b/src/shared/proparser/qmakevfs.cpp
@@ -49,11 +49,29 @@ QMakeVfs::QMakeVfs()
 #ifndef QT_NO_TEXTCODEC
     m_textCodec = 0;
 #endif
+#ifdef PROEVALUATOR_THREAD_SAFE
+    QMutexLocker locker(&s_mutex);
+#endif
+    ++s_refCount;
 }
 
+QMakeVfs::~QMakeVfs()
+{
+#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;
@@ -111,16 +129,6 @@ 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/src/shared/proparser/qmakevfs.h b/src/shared/proparser/qmakevfs.h
index da0d0626d8f..34dd96fd7b7 100644
--- a/src/shared/proparser/qmakevfs.h
+++ b/src/shared/proparser/qmakevfs.h
@@ -72,10 +72,10 @@ public:
     Q_DECLARE_FLAGS(VfsFlags, VfsFlag)
 
     QMakeVfs();
+    ~QMakeVfs();
 
     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);
@@ -93,6 +93,7 @@ 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).