read_bytes:sslv3 alert certificate unknown - what does this mean?

[neilyoung]

My intention is to forward https://localhost (self-signed) to http://localhost:400
Basically it works, but the error concerns me.

{"level":50,"time":1584352037638,"pid":21962,"hostname":"myhost","name":"redbird","msg":"HTTPS Client  Error","stack":"Error: 4549135808:error:14094416:SSL routines:ssl3_read_bytes:sslv3 alert certificate unknown:../deps/openssl/openssl/ssl/record/rec_layer_s3.c:1544:SSL alert number 46\n","type":"Error","v":1}

Reverse proxy script:

var redbird = new require('redbird')({
	port: 80,
	ssl: {
		port: 443,
		key: "dev-key.pem",
		cert: "dev-cert.pem",
	}
});

redbird.register('localhost', 'http://localhost:4000', {ssl: { redirect: false}});