google-api-dotnet-client: GetAccessTokenForRequestAsync response token missing kid in header

I have been converting code from Java version to .NET version.

Issue we ran into is that when we get a bearer token for API calls, the .NET version is missing the “kid” field in the header of the JWT token. Otherwise token is valid.

.NET :

_credentials = ServiceAccountCredential.FromServiceAccountData(File.OpenRead(serviceAccountFile));
_token = _credentials.GetAccessTokenForRequestAsync(_audience).Result;

Java :

ServiceAccountJwtAccessCredentials credentials = null;
credentials = ServiceAccountJwtAccessCredentials.fromStream( new FileInputStream( accountFile ),
        new URI( audience ) );
String token = credentials.getRequestMetadata( ).get( HttpHeaders.AUTHORIZATION )
        .get( 0 );

Tokens are otherwise identical and correct. However, the missing kid field is causing error. Both audience and account file are the same.

Are we doing something wrong here, is there a bug in the GetAccessTokenForRequestAsync function?