MultipartFile - filename not available in content disposition

I've created MultipartFile as follows. When I post this to API, the file name parameter is not available in content disposition.

Future<MultipartFile> imageDetails = http.MultipartFile.fromPath('file', '/resources/test.png',

contentType: MediaType('image', 'png'), filename: 'test.png');

The server code expects for the filename parameters from the content disposition.

If I make a call to same API using Postman or Java REST client. This works well.

However, this fails with dart code.

Can someone please help me out here.

Thanks

Harshad