Eloquent cannot save or delete models with composite primary keys

[lazlo-bonin]

When defining composite primary keys then calling save or delete on an instanced model, an exception is thrown.

Save

Type: ErrorException
Message: PDO::lastInsertId() expects parameter 1 to be string, array given
File: /vendor/laravel/framework/src/Illuminate/Database/Query/Processors/Processor.php
Line: 32

Delete

Type: ErrorException
Message: array_key_exists(): The first argument should be either a string or an integer
File: /vendor/laravel/framework/src/Illuminate/Database/Eloquent/Model.php
Line: 2324

I suspect Eloquent is expecting a string primary key, while an array is given.