Inputmask: Mask with two optional parts doesn't work as expected

[mattsones]

I'm trying to mask a 7 or 10 digit phone number with an optional extension.

Goal:

input --> result
1234567 --> 123-4567
1234567890 --> [phone]
12345678901234 --> [phone] x1234

Here's my attempt:

$("input").inputmask({
            "mask": "[(999) ]999-9999[ x99999]",
            // "numericInput": true,
            "skipOptionalPartCharacter": " ",
            "greedy": false
        });

Result
1234567 --> (123) 456-7___
1234567890 --> [phone]
12345678901234 --> [phone] x1234

If I turn numeric input on, I get the reverse problem:
1234567 --> ___-__12 x34567
1234567890 --> __1-2345 x67890
12345678901234 --> (_12) 345-6789 x01234

How can I get the desired result?

[mattsones]

I was able to find a workaround with multiple masks:

$("input").inputmask({
  "mask": ["999-9999","[phone][ x9{1,5}]"],
  "greedy": false
});