tkdnd does not work on children widgets

i tried using tkdnd on a widget which is the child of a frame widget, but it does not work

`package require tkdnd`
`frame .f`
`listbox .f.l`

`pack .f`
`pack .f.l`

`tkdnd::drop_target register .f.l *`
`bind .f.l <<Drop>> {put %D; return %A}`

If i drag a file to the listbox widget not happen, i have also tried this on other widget and it does not work
