Bad XMLHttpRequest when uploading to S3

I'm using Evaporate.js to upload files to S3. I've had everything working, until I decided to enable server side encryption.

According to the S3 docs, you can enable it by passing a header. So I updated my add code to look like:

var promise = _e_.add({
            name: name,
            file: files[i],
            started: callback_methods.started,
            complete: callback_methods.complete,
            cancelled: callback_methods.cancelled,
            progress: callback_methods.progress,
            error: callback_methods.error,
            warn: callback_methods.warn,
            paused: callback_methods.paused,
            pausing: callback_methods.pausing,
            resumed: callback_methods.resumed,
            nameChanged: callback_methods.nameChanged,
            xAmzHeadersAtInitiate: { 'x-amz-server-side​-encryption': 'AES256'} // THIS IS THE ONLY LINE THAT CHANGED!!!
          }
          )

I get the error: DOMException: Failed to execute 'setRequestHeader' on 'XMLHttpRequest': 'AWS4-HMAC-SHA256 Credential=XXXXXXXXXXXXXXX/XXXXXXX/us-east-1/s3/aws4_request, SignedHeaders=content-type;host;x-amz-date;x-amz-server-side​-encryption, Signature=XXXXXXXXXXXXXXXXXXXXX' is not a valid HTTP header field value.