function finishMintingInternal(address _minter)
    public returns (bool)
  {
    uint256 lotId = minterLotIds[_minter];
    MintableLot storage lot = mintableLots[lotId];
    require(lot.minters[_minter], "TM17");

    lot.minters[_minter] = false;
    lot.activeMinters--;

    if (lot.activeMinters == 0 && lot.mintableSupply == 0) {
      finishLotMintingPrivate(lotId);
    }
    return true;
  }