JSON-LD Playground and @context URLs

When I'm using the JSON-LD Playground, this:

  "@context": "https://iotdb.org/pub/iot",

Gives me the message

Dereferencing a URL did not result in a valid JSON-LD object. Possible
causes are an inaccessible URL perhaps due to a same-origin policy (ensure
the server uses CORS if you are using client-side JavaScript), too many
redirects, a non-JSON response, or more than one HTTP Link Header was
provided for a remote context

But it seems to be valid:


$ curl 'https://iotdb.org/pub/iot' --header 'Accept: application/ld+json'
--include

HTTP/1.1 302 FOUND

Date: Mon, 08 Jun 2015 18:43:41 GMT

Server: Apache/2.2.25 (Unix) DAV/2 PHP/5.2.16 mod_ssl/2.2.25
OpenSSL/0.9.8e-fips-rhel5 mod_fastcgi/2.4.6

X-Frame-Options: SAMEORIGIN

Location: https://iotdb.org/pub/iot.jsonld

Transfer-Encoding: chunked

Content-Type: text/html; charset=utf-8


And

$ curl 'https://iotdb.org/pub/iot.jsonld' --include | head

HTTP/1.1 200 OK

Date: Mon, 08 Jun 2015 18:43:22 GMT

Server: Apache/2.2.25 (Unix) DAV/2 PHP/5.2.16 mod_ssl/2.2.25
OpenSSL/0.9.8e-fips-rhel5 mod_fastcgi/2.4.6

Last-Modified: Tue, 10 Mar 2015 14:15:19 GMT

ETag: "c1d8e3c-2824-510efc7cecbc0"

Accept-Ranges: bytes

Content-Length: 10276

Content-Type: application/ld+json


Any thoughts?