Cannot set properties of undefined (setting 'Symbol(lte)')

Ao utilizar o operador Op.gte ele captura normal, porém ao utilizar Op.lte ele me estoura a stack trace:

D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\api\controllers\TurmaController.js:11
    data_final ? where.data_final[Op.lte] = data_final : null
                                          ^

TypeError: Cannot set properties of undefined (setting 'Symbol(lte)')
    at pegaTodasAsTurmas (D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\api\controllers\TurmaController.js:11:43)
    at Layer.handle [as handle_request] (D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\node_modules\express\lib\router\layer.js:95:5)
    at next (D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\node_modules\express\lib\router\route.js:144:13)
    at Route.dispatch (D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\node_modules\express\lib\router\route.js:114:3)
    at Layer.handle [as handle_request] (D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\node_modules\express\lib\router\layer.js:95:5)
    at D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\node_modules\express\lib\router\index.js:284:15
    at Function.process_params (D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\node_modules\express\lib\router\index.js:346:12)
    at next (D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\node_modules\express\lib\router\index.js:280:10)
    at Function.handle (D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\node_modules\express\lib\router\index.js:175:3)
    at router (D:\projetos\Alura\orm-nodejs-api-sequelize-mysql2\node_modules\express\lib\router\index.js:47:12)

meu controller:

static async pegaTodasAsTurmas(req, res){
    const {data_inicial, data_final} = req.query
    const where = {}
    data_inicial || data_final ? where.data_inicial = {} : null
    data_inicial ? where.data_inicial[Op.gte] = data_inicial : null
    data_final ? where.data_final[Op.lte] = data_final : null
    try {
      const todasAsTurmas = await database.Turmas.findAll({ where })
      return res.status(200).json(todasAsTurmas)  
    } catch (error) {
      return res.status(500).json(error.message)
    }
  }

Repositorio: https://github.com/IgorMartinsOli/orm-nodejs-api-sequelize-mysql