Are key case sensitive in request.header.host in lambda edge function (nodejs16.x)

Question

I have a scenario where I want to switch to an s3 origin based on some condition,

if (condition) {
        request.headers.host = [{key: "**Host**", value: 'some_s3_origin'}];
    }

I wanted to confirm if the value for "key" is case in-sensitive or not id the above condition same as

if (condition) {
        request.headers.host = [{key: "**host**", value: 'some_s3_origin'}];
    }