Why does phpunit's check for the passed arguments fail when I use named arguments?

I have a simple test where I mock a dependency of the code under test:

<?php

use PHPUnit\Framework\TestCase;

class Dependency {
    public function someFunction(int $first, int $second): int {
        return $first + $second;
    }
}

class CodeUnderTest {
    public function testMe(Dependency $dep, int $first, int $second): int {
        return $dep->someFunction($first, $second);
    }
}

class TheTest extends TestCase
{
    public final function testMe(): void {
        $dep = $this->createMock(Dependency::class);
        $dep->expects(self::once())->method('someFunction')->with(second: 2, first: 1)->willReturn(3);
        $codeUnderTest = new CodeUnderTest();
        $codeUnderTest->testMe($dep, 1, 2);
    }
}

This fails:

Expectation failed for method name is "someFunction" when invoked 1 time(s)
Parameter 0 for invocation Dependency::someFunction(1, 2): int does not match expected value.
Failed asserting that 1 matches expected 2.
Expected :2
Actual   :1

Why does this happen? My mock object clearly defines the expected values, even by name.

Looks like phpunit does not handle named arguments and silently ignores them.

$dep->expects(self::once())->method('someFunction')->with(1, 2)->willReturn(3);

makes the test pass.

With that it's probably better to not use named arguments in the with call.