HTTP data fetcher- Headers not passed through to getRequestHeaders()

I'm making a JSON migration and it requires the header: Accept: 'application/json; charset=utf-8'

Here's my source configuration:
source:
plugin: url
data_fetcher_plugin: http
data_parser_plugin: json
authentication:
plugin: basic
username: ''
password: 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX'
headers:
Accept: 'application/json; charset=utf-8'
Content-Type: 'application/json'
urls: https://www.example.com/jsonfeed

The authentication works, but the headers aren't passed though to getRequestHeaders()

The following patch fixes it for me, but I'm not sure whether this is a bug or not.

Here's what I've done:

Index: httpdocs/modules/contrib/migrate_plus/src/Plugin/migrate_plus/data_fetcher/Http.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- httpdocs/modules/contrib/migrate_plus/src/Plugin/migrate_plus/data_fetcher/Http.php (date 1485957865000)
+++ httpdocs/modules/contrib/migrate_plus/src/Plugin/migrate_plus/data_fetcher/Http.php (revision )
@@ -70,7 +70,7 @@
* {@inheritdoc}
*/
public function getRequestHeaders() {
- return !empty($this->headers) ? $this->headers : [];
+ return !empty($this->configuration['headers']) ? $this->configuration['headers'] : [];
}

/**