ext.msg.show changing defaults

Code:

Ext.Msg.show({
                title: 'Validation',
                message: message,
                height: 300,
                scrollable: true,
                buttons: Ext.MessageBox.OK
            });

I'm having a problem with this bit of code. For this particular message box I want the height to be 300 and scrollable to be true because message is quite large. However after this is called any message box (confirm, alert, prompt) seem to inherit both the height and scrollable values which I do not want. Is there a way around this?