Implement Keyboard focus on a custom morph when have rounded corners

I´m developing new widgets, integrateds in Polymorph. But when I try implement the keyboard focus appearance fails when the widget have rounded corners:



I imagine something miss, but I don´t know what.

I implement the keyboard focus with

drawSubmorphsOn: aCanvas

        super drawSubmorphsOn: aCanvas.
        self hasKeyboardFocus ifTrue: [self drawKeyboardFocusOn: aCanvas].

Many thanks for the help  :))