Index: wp-admin/includes/file.php
 ===================================================================
 --- /var/www/html/src/wp-admin/includes/file.php	(revision 38260)
 +++ /var/www/html/src/wp-admin/includes/file.php	(working copy)
 @@ -1260,7 +1260,7 @@
  ?>
  	<p class="request-filesystem-credentials-action-buttons">
  		<button class="button cancel-button" data-js-action="close" type="button"><?php _e( 'Cancel' ); ?></button>
 -		<?php submit_button( __( 'Proceed' ), 'button', 'upgrade', false ); ?>
 +		<?php submit_button( __( 'Proceed' ), 'button button-primary', 'upgrade', false ); ?>
  	</p>
  </div>
  </form>