Composer require ... 的报错

执行 composer require predis/predis 时的错误：

vagrant@homestead:~/code/larabbs2$ composer require predis/predis
Using version ^1.1 for predis/predis
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)
Nothing to install or update
Generating optimized autoload files
PHP Fatal error:  Uncaught TypeError: Argument 1 passed to Composer\Autoload\ClassLoader::addClassMap() must be of the type array, integer given, called in phar:///usr/local/bin/composer/src/Composer/Autoload/AutoloadGenerator.php on line 760 and defined in phar:///usr/local/bin/composer/vendor/composer/ClassLoader.php:92
Stack trace:
#0 phar:///usr/local/bin/composer/src/Composer/Autoload/AutoloadGenerator.php(760): Composer\Autoload\ClassLoader->addClassMap(1)
#1 phar:///usr/local/bin/composer/src/Composer/Autoload/AutoloadGenerator.php(303): Composer\Autoload\AutoloadGenerator->getStaticFile('f5db2233242cfba...', '/home/vagrant/c...', '/home/vagrant/c...', '/home/vagrant/c...', 50600)
.
.
.

查找后发现了这个帖子：分享：Composer dumpautoload 出现一大堆错误
执行rm -rf vendor/composer/autoload_*之后，composer就正常了。
但是下一次，又会出现这个问题，需要在删一次文件，然后就又正常了。

每次出问题的时候 ./vendor/composer/autoload_classmap.php，就会变成一个空文件。
这该怎么解决呢？