Communications.makeWebRequest() returning -200 (Invalid request header fields)?

Hello!

I've recently started working on a watch app that makes a web request to a third party API. After plenty of fiddling however, I have landed on this error that I can't seem to figure out.

Here is a copy of the code I'm using. I've edited the sample WebRequest project that comes with the SDK installation to meet my needs:

function makeRequest() as Void {
        var url = "https://api-link-here/"
            + path-param-here +
            "/rest-of-api-link-here";

        var params = null;

        var options = {
            :method => Communications.HTTP_REQUEST_METHOD_GET,
            :headers => {
                "Content-Type" => REQUEST_CONTENT_TYPE_JSON,
                "Authorization" => authorization-token-here,                                               // set headers
                "APIVersion" => api-version-here},
            :responseType => Communications.HTTP_RESPONSE_CONTENT_TYPE_JSON
        };

        Communications.makeWebRequest(url, params, options, method(:onReceive));
    }

    function onReceive(responseCode as Number, data as Dictionary?) as Void {
        if (responseCode == 200) {
            System.println("Request Successful");                   // print success
        } else {
            System.println("Response: " + responseCode);            // print response code
        }
    }

I call the makeRequest() method from a BehaviorDelegate but am presented with a Response: -200 error code in the Debug Output. This indicates that my request header fields are invalid.

I have included 3 header fields. The APIVersion header field is one required by this particular third party API.

Does anybody have any idea what I'm doing wrong - I suspect it's a syntax error somewhere in my code.

Thanks in advance!