Bamboo API wrongly expecting java.util.ArrayList values in POST request data

I’m trying to make a request exactly as show in post api latest queue. Nevertheless, if payload fields are included (i.e. fakeParam), the request fails with response:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?><status><status-code>400</status-code><message>Can not deserialize instance of java.util.ArrayList out of VALUE_STRING token
 at [Source: org.apache.catalina.connector.CoyoteInputStream@10a65620; line: 1, column: 2]</message></status>

This points to the string expected to rather be a a list. The request succeeds if I change the payload to {"fakeParam":["<string>"]}, proving the point. Nevertheless, I have no control over the format of the parameters that my client application sends, so I can’t modify them or empty them.

Is this a bug? Any ideas how to get around it?