diff --git a/kcmkwin/kwinrules/main.cpp b/kcmkwin/kwinrules/main.cpp
index 4a70a8970d..bb4b8cae96 100644
--- a/kcmkwin/kwinrules/main.cpp
+++ b/kcmkwin/kwinrules/main.cpp
@@ -76,15 +76,15 @@ static Rules* findRule( const QList< Rules* >& rules, Window wid, bool whole_app
         NET::WM2WindowClass | NET::WM2WindowRole | NET::WM2ClientMachine );
     if( !info.valid()) // shouldn't really happen
         return NULL;
-    QByteArray wmclass_class = info.windowClassClass().lower();
-    QByteArray wmclass_name = info.windowClassName().lower();
-    QByteArray role = info.windowRole().lower();
+    QByteArray wmclass_class = info.windowClassClass().toLower();
+    QByteArray wmclass_name = info.windowClassName().toLower();
+    QByteArray role = info.windowRole().toLower();
     NET::WindowType type = info.windowType( NET::NormalMask | NET::DesktopMask | NET::DockMask
         | NET::ToolbarMask | NET::MenuMask | NET::DialogMask | NET::OverrideMask | NET::TopMenuMask
         | NET::UtilityMask | NET::SplashMask );
     QString title = info.name();
 //    QCString extrarole = ""; // TODO
-    QByteArray machine = info.clientMachine().lower();
+    QByteArray machine = info.clientMachine().toLower();
     Rules* best_match = NULL;
     int match_quality = 0;
     for( QList< Rules* >::ConstIterator it = rules.begin();
diff --git a/main.cpp b/main.cpp
index 8550079684..dd26923009 100644
--- a/main.cpp
+++ b/main.cpp
@@ -194,7 +194,7 @@ KDE_EXPORT int kdemain( int argc, char * argv[] )
 	// manager, since the session manager will register multiple kwins,
         // one for each screen...
         QByteArray multiHead = getenv("KDE_MULTIHEAD");
-        if (multiHead.lower() == "true") 
+        if (multiHead.toLower() == "true") 
             {
 
             Display* dpy = XOpenDisplay( NULL );
diff --git a/manage.cpp b/manage.cpp
index bd22726b43..35fd1674a7 100644
--- a/manage.cpp
+++ b/manage.cpp
@@ -86,8 +86,8 @@ bool Client::manage( Window w, bool isMapped )
         {
         // Qt3.2 and older had this all lowercase, Qt3.3 capitalized resource class
         // force lowercase, so that workarounds listing resource classes still work
-        resource_name = QByteArray( classHint.res_name ).lower();
-        resource_class = QByteArray( classHint.res_class ).lower();
+        resource_name = QByteArray( classHint.res_name ).toLower();
+        resource_class = QByteArray( classHint.res_class ).toLower();
         XFree( classHint.res_name );
         XFree( classHint.res_class );
         }