diff --git a/src/corelib/codecs/qtextcodec.cpp b/src/corelib/codecs/qtextcodec.cpp
index c9fbec8..2ce2543 100644
--- a/src/corelib/codecs/qtextcodec.cpp
+++ b/src/corelib/codecs/qtextcodec.cpp
@@ -1473,6 +1473,26 @@ QString QTextCodec::toUnicode(const char *chars) const
     return convertToUnicode(chars, len, 0);
 }
 
+void QTextCodec::destroyCodecsForMib(int mib)
+{
+    if (!all)
+        return;
+
+#ifndef QT_NO_THREAD
+    QMutexLocker locker(textCodecsMutex());
+#endif
+
+    QList<QTextCodec*>::iterator itr = all->begin();
+    while (itr != all->end()) {
+        QTextCodec *tc = *itr;
+        if (tc->mibEnum() == mib) {
+            itr = all->erase(itr);
+            delete tc;
+        } else {
+            ++itr;
+        }
+    }
+}
 
 /*!
     \class QTextEncoder
diff --git a/src/corelib/codecs/qtextcodec.h b/src/corelib/codecs/qtextcodec.h
index 4ba8b85..f4e59f1 100644
--- a/src/corelib/codecs/qtextcodec.h
+++ b/src/corelib/codecs/qtextcodec.h
@@ -59,6 +59,8 @@ class QIODevice;
 class QTextDecoder;
 class QTextEncoder;
 
+class QLibraryPrivate;
+
 class Q_CORE_EXPORT QTextCodec
 {
     Q_DISABLE_COPY(QTextCodec)
@@ -147,8 +149,10 @@ public:
 
 private:
     friend class QTextCodecCleanup;
+    friend class QLibraryPrivate;
     static QTextCodec *cftr;
     static bool validCodecs();
+    static void destroyCodecsForMib(int mib);
 };
 Q_DECLARE_OPERATORS_FOR_FLAGS(QTextCodec::ConversionFlags)
 
diff --git a/src/corelib/plugin/qfactoryloader.cpp b/src/corelib/plugin/qfactoryloader.cpp
index a26dcd8..4517a78 100644
--- a/src/corelib/plugin/qfactoryloader.cpp
+++ b/src/corelib/plugin/qfactoryloader.cpp
@@ -67,7 +67,7 @@ public:
     ~QFactoryLoaderPrivate();
     mutable QMutex mutex;
     QByteArray iid;
-    QList<QLibraryPrivate*> libraryList;
+    mutable QList<QPair<QLibraryPrivate*, bool> > libraryList;
     QMap<QString,QLibraryPrivate*> keyMap;
     QStringList keyList;
     QString suffix;
@@ -79,8 +79,12 @@ public:
 
 QFactoryLoaderPrivate::~QFactoryLoaderPrivate()
 {
-    for (int i = 0; i < libraryList.count(); ++i)
-        libraryList.at(i)->release();
+    for (int i = 0; i < libraryList.count(); ++i) {
+        if (libraryList.at(i).second)
+            libraryList.at(i).first->unload();
+
+        libraryList.at(i).first->release();
+    }
 }
 
 QFactoryLoader::QFactoryLoader(const char *iid,
@@ -135,6 +139,7 @@ void QFactoryLoader::update()
                 library->release();
                 continue;
             }
+            bool did_load = false;
             QString regkey = QString::fromLatin1("Qt Factory Cache %1.%2/%3:/%4")
                              .arg((QT_VERSION & 0xff0000) >> 16)
                              .arg((QT_VERSION & 0xff00) >> 8)
@@ -154,6 +159,7 @@ void QFactoryLoader::update()
                     library->release();
                     continue;
                 }
+                did_load = true;
                 QObject *instance = library->instance();
                 if (!instance)
                     // ignore plugins that have a valid signature but cannot be loaded.
@@ -176,7 +182,7 @@ void QFactoryLoader::update()
                 library->release();
                 continue;
             }
-            d->libraryList += library;
+            d->libraryList += QPair<QLibraryPrivate*, bool>(library, did_load);
             for (int k = 0; k < keys.count(); ++k) {
                 // first come first serve, unless the first
                 // library was built with a future Qt version,
@@ -233,13 +239,24 @@ QObject *QFactoryLoader::instance(const QString &key) const
 
     QString lowered = d->cs ? key : key.toLower();
     if (QLibraryPrivate* library = d->keyMap.value(lowered)) {
-        if (library->instance || library->loadPlugin()) {
-            if (QObject *obj = library->instance()) {
-                if (obj && !obj->parent())
-                    obj->moveToThread(QCoreApplicationPrivate::mainThread());
-                return obj;
+        if (!library->instance) {
+            if (!library->loadPlugin())
+                return 0;
+
+            QList<QPair<QLibraryPrivate*, bool> >::iterator itr;
+            for (itr = d->libraryList.begin(); itr != d->libraryList.end(); ++itr) {
+                if (library == (*itr).first) {
+                    (*itr).second = true;   // mark this plugin as loaded
+                    break;
+                }
             }
         }
+
+        if (QObject *obj = library->instance()) {
+            if (obj && !obj->parent())
+                obj->moveToThread(QCoreApplicationPrivate::mainThread());
+            return obj;
+        }
     }
     return 0;
 }
diff --git a/src/corelib/plugin/qlibrary.cpp b/src/corelib/plugin/qlibrary.cpp
index 1874a9e..de6cd5c 100644
--- a/src/corelib/plugin/qlibrary.cpp
+++ b/src/corelib/plugin/qlibrary.cpp
@@ -61,6 +61,8 @@
 #include <qdebug.h>
 #include <qvector.h>
 #include <qdir.h>
+#include <qtextcodecplugin.h>
+#include <qtextcodec.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -451,8 +453,21 @@ bool QLibraryPrivate::unload()
     if (!pHnd)
         return false;
     if (!libraryUnloadCount.deref()) { // only unload if ALL QLibrary instance wanted to
-        if (instance)
-            delete instance();
+        if (instance) {
+            QObject *obj = instance();
+            if (QTextCodecPlugin *tcPlugin = qobject_cast<QTextCodecPlugin *>(obj)) {
+                // delete all text codecs created from this text codec plugin
+                QList<int> listMibs = tcPlugin->mibEnums();
+                QList<int>::const_iterator itr = listMibs.constBegin();
+                while (itr != listMibs.constEnd()) {
+                    QTextCodec::destroyCodecsForMib(*itr);
+                    ++itr;
+                }
+            }
+
+            delete obj;
+        }
+
         if  (unload_sys()) {
             instance = 0;
             pHnd = 0;