Change in return value of setTimeout #35770

• 12.19.0:
• all:

What steps will reproduce the bug?

In node:12.19.0-slim docker image setTimeout function returns a value for which isNaN=false
In node:12.18.4-slim docker image setTimeout function returns a value for which isNaN=true

timeoutId = setTimeout(function() {alert("Timeout")}, 1000);
console.log(isNaN(timeoutId))

Is this an intentional behaviour?