Problem with dialing extension digits

How can you dial more than one extension digit?

I am trying to transfer to a number with an extension.
I accept a number formatted like 555-555-5555x1234.

The following is my configuration for my dial options, both with the same result.

D(w1234)
D(w1w2w3w4)
D(w1),D(w2),D(w3),D(w4)

All lead to it dialing a single digit, when the other end picks up.