Unable to delete key from a json in karate framework - remove() and delete did not work

I want to delete a key from JSON. I found two examples shared by @Peter Thomas. I tried both and unfortunately, none worked.

Example 1

* def json = { a: 1, b: 2 }
* def key = 'b'
* if (true) karate.remove('json', key)
* match json == { a: 1 }

Error javascript evaluation failed: if (true) karate.remove('json', key), unexpected path: b

Example 2

* def json = { a: 1, b: 2 }
* def key = 'b'
* if (true) delete json[key]
* match json == { a: 1 }

Error actual: {a=1, b=2}, expected: {a=1}, reason: actual value has 1 more key(s) than expected: {b=2}