Laravel外键不正确

I'm having some trouble with migrations in Laravel. I keep getting the error that the foreign key constraint is illformed. I can't seem to see what I do wrong either. Naming the migrations so they run in the right order is in place. I also tried running one and one migration, and it always stops on the second migration (municipalities).

What am I doing wrong here?

1st table: counties

    public function up()
    {
        Schema::create('counties', function (Blueprint $table) {
            $table->bigIncrements('id')->unsigned();
            $table->string('name');
            $table->timestamps();
        });
        DB::statement('ALTER TABLE counties CHANGE id id INT(2) UNSIGNED ZEROFILL NOT NULL');
    }

2nd table: municipalities

public function up()
{
    Schema::create('municipalities', function (Blueprint $table) {
        $table->bigIncrements('id')->unsigned();
        $table->bigInteger('county_id')->unsigned();
        $table->foreign('county_id')->references('id')->on('counties')->onDelete('cascade');
        $table->string('name');
        $table->timestamps();
    });
    DB::statement('ALTER TABLE municipalities CHANGE county_id county_id INT(2) UNSIGNED ZEROFILL NOT NULL');
    DB::statement('ALTER TABLE municipalities CHANGE id id INT(4) UNSIGNED ZEROFILL NOT NULL');
}

3rd table: postals

public function up()
{
    Schema::create('postals', function (Blueprint $table) {
        $table->bigIncrements('id')->unsigned();
        $table->bigInteger('municipality_id')->unsigned();
        $table->foreign('municipality_id')->references('id')->on('municipalities')->onDelete('cascade');
        $table->string('name');
        $table->timestamps();
    });
    DB::statement('ALTER TABLE postals CHANGE municipality_id municipality_id INT(4) UNSIGNED ZEROFILL NOT NULL');
    DB::statement('ALTER TABLE postals CHANGE id id INT(6) UNSIGNED ZEROFILL NOT NULL');
}

4th table: zips

public function up()
{
    Schema::create('zips', function (Blueprint $table) {
        $table->bigIncrements('id')->unsigned();
        $table->bigInteger('postal_id')->unsigned();
        $table->foreign('postal_id')->references('id')->on('postals')->onDelete('cascade');
        $table->decimal('lat', 12, 7);
        $table->decimal('lon', 12, 7);
        $table->timestamps();
    });
    DB::statement('ALTER TABLE zips CHANGE id id INT(4) UNSIGNED ZEROFILL NOT NULL');
    DB::statement('ALTER TABLE zips CHANGE postal_id postal_id INT(6) UNSIGNED ZEROFILL NOT NULL');
}

And the error message I'm getting:

Apparantly I can't use bigInteger when creating the foreign keys. Switched to normal integer and it works