diff --git a/kstyle/oxygenshadowhelper.cpp b/kstyle/oxygenshadowhelper.cpp
--- a/kstyle/oxygenshadowhelper.cpp
+++ b/kstyle/oxygenshadowhelper.cpp
@@ -55,7 +55,10 @@
     ShadowHelper::~ShadowHelper( void )
     {
 
-        qDeleteAll( _shadows );
+        // qDeleteAll doesn't make containers detach so make a copy explicitly
+        const QMap<QWidget*, KWindowShadow*> shadows = _shadows;
+        qDeleteAll( shadows );
+
         delete _shadowCache;
 
     }