Loading state management not triggered

[anzuj]

I'm having some trouble indicating that the sheet download is being prepared on the background. My code:

    <download-excel
      :data="currentDataset.items"
      :fields="exportFields"
      :worksheet="currentDataset.name"
      :name="currentDataset.name + '.xls'"
      :before-generate="(downloadingSheet = true)"
      :before-finish="(downloadingSheet = false)"
    >
      <v-btn :loading="downloadingSheet">Download Excel </v-btn>
    </download-excel>

It seems though, that the local data value downloadingSheet is not changed via :before-generate and :before-finish, it remains the initial state false. What am I doing wrong?