HTTP COPY returning 404

I can't seem to get the HTTP COPY working. It appears to be supported in the source. I've tried:

curl -i -X COPY -H"Destination: https://example.net/bar" https://example.org/foo

as well as:

var http = new XMLHttpRequest();
http.open('COPY', 'https://example.org/foo');
http.setRequestHeader('Destination', 'https://example.net/bar');
http.withCredentials = true;
http.onreadystatechange = function() {
  if (this.readyState == this.DONE) {
    console.log(this.getAllResponseHeaders());
  }
};
http.send();

In both cases, I get a 404. Example response from curl:

HTTP/1.1 404 Not Found
Accept-Patch: application/json, application/sparql-update
Accept-Post: text/turtle, application/json
Access-Control-Allow-Credentials: true
Access-Control-Expose-Headers: User, Location, Link, Vary, Last-Modified, WWW-Authenticate, Content-Length, Accept-Patch, Accept-Post, Allow, Updates-Via, Ms-Author-Via
Access-Control-Max-Age: 1728000
Allow: OPTIONS, HEAD, GET, PATCH, POST, PUT, MKCOL, DELETE, COPY, MOVE, LOCK, UNLOCK
Link: <https://example.org/foo,acl>; rel="acl", <https://example.org/foo,meta>; rel="meta"
Ms-Author-Via: DAV, SPARQL
Updates-Via: wss://example.org/
User: 
Date: Sun, 03 Jan 2016 00:07:24 GMT
Content-Length: 9
Content-Type: text/plain; charset=utf-8

Not Found

The User header has my WebID in the XHR case if I'm authenticated.

https://example.org/foo sure does exist. I've even explicitly set https://example.org/foo,acl (for public r-w-a), still no go.

linkeddata / gold

HTTP COPY returning 404 #63