diff --git a/kmcomposewin.cpp b/kmcomposewin.cpp
index eb8f00925..49c68eaba 100644
--- a/kmcomposewin.cpp
+++ b/kmcomposewin.cpp
@@ -194,7 +194,7 @@ KMComposeWin::KMComposeWin( KMMessage *aMsg, uint id  )
     mAutoSaveTimer( 0 ), mLastAutoSaveErrno( 0 )
 {
   (void) new MailcomposerAdaptor( this );
-  QDBusConnection::sessionBus().registerObject("/Composer", this);         
+  QDBusConnection::sessionBus().registerObject("/Composer", this);
   mClassicalRecipients = GlobalSettings::self()->recipientsEditorType() ==
     GlobalSettings::EnumRecipientsEditorType::Classic;
 
@@ -770,9 +770,9 @@ void KMComposeWin::slotView(void)
 
   //This sucks awfully, but no, I cannot get an activated(int id) from
   // actionContainer()
-  if ( sender()->metaObject()->className() != "KToggleAction")
+  KToggleAction *act = ::qobject_cast<KToggleAction *>( sender() );
+  if ( !act )
     return;
-  KToggleAction *act = (KToggleAction *) sender();
 
   if (act == mAllFieldsAction)
     id = 0;
diff --git a/kmfoldercachedimap.cpp b/kmfoldercachedimap.cpp
index 105badad7..30894933e 100644
--- a/kmfoldercachedimap.cpp
+++ b/kmfoldercachedimap.cpp
@@ -1572,7 +1572,7 @@ void KMFolderCachedImap::slotProgress(unsigned long done, unsigned long total)
 
 void KMFolderCachedImap::setAccount(KMAcctCachedImap *aAccount)
 {
-  assert( aAccount->metaObject()->className() == "KMAcctCachedImap" );
+  assert( ::qobject_cast<KMAcctCachedImap *>(aAccount) );
   mAccount = aAccount;
   if( imapPath()=="/" ) aAccount->setFolder( folder() );
 
diff --git a/kmfoldertree.cpp b/kmfoldertree.cpp
index 07d0a1832..370ecdb58 100644
--- a/kmfoldertree.cpp
+++ b/kmfoldertree.cpp
@@ -1648,7 +1648,7 @@ bool KMFolderTree::eventFilter( QObject *o, QEvent *e )
 {
   if ( e->type() == QEvent::MouseButtonPress &&
       static_cast<QMouseEvent*>(e)->button() == Qt::RightButton &&
-       QString(o->metaObject()->className()) == "Q3Header" )
+       ::qobject_cast<Q3Header *>(o) )
   {
     mPopup->popup( static_cast<QMouseEvent*>(e)->globalPos() );
     return true;
diff --git a/kmheaders.cpp b/kmheaders.cpp
index c33a6efa1..2611837eb 100644
--- a/kmheaders.cpp
+++ b/kmheaders.cpp
@@ -254,7 +254,7 @@ bool KMHeaders::eventFilter ( QObject *o, QEvent *e )
 {
   if ( e->type() == QEvent::MouseButtonPress &&
       static_cast<QMouseEvent*>(e)->button() == Qt::RightButton &&
-      QString(o->metaObject()->className()) == "Q3Header" )
+       ::qobject_cast<Q3Header *>(o) )
   {
     // if we currently only show one of either sender/receiver column
     // modify the popup text in the way, that it displays the text of the other of the two
@@ -1321,9 +1321,11 @@ void KMHeaders::setStyleDependantFrameWidth()
 {
   // set the width of the frame to a reasonable value for the current GUI style
   int frameWidth;
-  if( style()->metaObject()->className() == "KeramikStyle" )
+#if 0 // is this hack still needed with kde4?
+  if( !qstrcmp( style()->metaObject()->className(), "KeramikStyle" ) )
     frameWidth = style()->pixelMetric( QStyle::PM_DefaultFrameWidth ) - 1;
   else
+#endif
     frameWidth = style()->pixelMetric( QStyle::PM_DefaultFrameWidth );
   if ( frameWidth < 0 )
     frameWidth = 0;
diff --git a/kmkernel.cpp b/kmkernel.cpp
index bb7f4ac89..3af0662a9 100644
--- a/kmkernel.cpp
+++ b/kmkernel.cpp
@@ -349,7 +349,7 @@ void KMKernel::openReader( bool onlyCheck )
 
   for ( QList<KMainWindow*>::const_iterator it = KMainWindow::memberList().begin();
        it != KMainWindow::memberList().end(); ++it ) {
-    if ( (*it)->metaObject()->className() == "KMMainWin" ) {
+    if ( ::qobject_cast<KMMainWin *>(*it) ) {
       ktmw = (*it);
       break;
     }
@@ -882,7 +882,7 @@ QStringList KMKernel::folderList() const
 
 QDBusObjectPath KMKernel::getFolder( const QString& vpath )
 {
-#if 0	
+#if 0
   QString adaptorName;
   const QString localPrefix = "/Local";
   if ( the_folderMgr->getFolderByURL( vpath ) )
@@ -899,7 +899,7 @@ QDBusObjectPath KMKernel::getFolder( const QString& vpath )
     QDBusConnection::sessionBus().registerObject( vpath, this );
     return QDBusObjectPath(vpath);
   }
-#endif  
+#endif
 #ifdef __GNUC__
 #warning Port DCOPRef usage!
 #endif
@@ -924,10 +924,10 @@ void KMKernel::raise()
   if (!iface.isValid() || !(reply = iface.call("newInstance")).isValid())
   {
        QDBusError err = iface.lastError();
-       kError() << "Communication problem with kmail" 
+       kError() << "Communication problem with kmail"
                  << "Error message was: " << err.name() << ": \"" << err.message() << "\"" << endl;
   }
- 
+
 }
 
 bool KMKernel::showMail( quint32 serialNumber, QString /* messageId */ )
@@ -1489,8 +1489,8 @@ void KMKernel::closeAllKMailWindows()
   KMainWindow *window = 0;
   while ( it.hasNext() ) {
     window = it.next();
-    if ( window && ( window->metaObject()->className() == "KMMainWindow" ||
-                     window->inherits("KMail::SecondaryWindow") ) )
+    if ( ::qobject_cast<KMMainWin *>(window) ||
+         ::qobject_cast<KMail::SecondaryWindow *>(window) )
     {
       window->setAttribute(Qt::WA_DeleteOnClose);
       window->close(); // close and delete the window
@@ -1918,7 +1918,7 @@ KMainWindow* KMKernel::mainWin()
   // First look for a KMMainWin.
   for ( QList<KMainWindow*>::const_iterator it = KMainWindow::memberList().begin();
        it != KMainWindow::memberList().end(); ++it )
-    if ( (*it)->metaObject()->className() == "KMMainWin" )
+    if ( ::qobject_cast<KMMainWin *>(*it) )
       return kmWin;
 
   // There is no KMMainWin. Use any other KMainWindow instead (e.g. in
diff --git a/kmmimeparttree.cpp b/kmmimeparttree.cpp
index f4f73a101..a9db7b08f 100644
--- a/kmmimeparttree.cpp
+++ b/kmmimeparttree.cpp
@@ -185,9 +185,11 @@ void KMMimePartTree::setStyleDependantFrameWidth()
 {
   // set the width of the frame to a reasonable value for the current GUI style
   int frameWidth;
-  if( style()->metaObject()->className() == "KeramikStyle" )
+#if 0 // is this hack still needed with kde4?
+  if( !qstrcmp( style()->metaObject()->className(), "KeramikStyle" ) )
     frameWidth = style()->pixelMetric( QStyle::PM_DefaultFrameWidth ) - 1;
   else
+#endif
     frameWidth = style()->pixelMetric( QStyle::PM_DefaultFrameWidth );
   if ( frameWidth < 0 )
     frameWidth = 0;
diff --git a/kmreaderwin.cpp b/kmreaderwin.cpp
index 6bae8ee10..15eb85ea7 100644
--- a/kmreaderwin.cpp
+++ b/kmreaderwin.cpp
@@ -1902,9 +1902,11 @@ void KMReaderWin::setStyleDependantFrameWidth()
     return;
   // set the width of the frame to a reasonable value for the current GUI style
   int frameWidth;
-  if( style()->metaObject()->className() == "KeramikStyle" )
+#if 0 // is this hack still needed with kde4?
+  if( !qstrcmp( style()->metaObject()->className(), "KeramikStyle" ) )
     frameWidth = style()->pixelMetric( QStyle::PM_DefaultFrameWidth ) - 1;
   else
+#endif
     frameWidth = style()->pixelMetric( QStyle::PM_DefaultFrameWidth );
   if ( frameWidth < 0 )
     frameWidth = 0;