Cannot print a response from WebSocket server

Gatling (Open-Source)
1

I’m using the following code:

.exec(ws("Open WS connection") .open("/${session_id}/socket?device=other")) .pause(2) .exec(ws("Get client browser id") .sendText("[]") .check(wsListen.within(10).until(1).jsonPath("$.[2]").saveAs("clientID")))

It does not report any failure. I assume it means that the check passed.
When I add

`
.exec{
session =>
println("clientID: " + session(“clientID”).as[String])
session
}

`

I get failure

[ERROR] i.g.c.a.b.SessionHookBuilder$$anon$1 - ‘hook-1’ crashed with ‘java.util.NoSuchElementException: key not found: clientID’, forwarding to the next one
This call works in JMeter. We like Gatling, but we cannot switch to it until WebSocket works for us.
Please help.