Multipart Input no longer treated with transfer encoding

Arbitrary multipart form action @Consumes(MediaType.MULTIPART_FORM_DATA) @Produces({ MediaType.APPLICATION_JSON, MediaType.MULTIPART_FORM_DATA }) Response doSomething(@MultipartForm DoSomethingRequest request); static class DoSomethingRequest { @FormParam( "myData" ) @PartType(MediaType.APPLICATION_OCTET_STREAM) private byte [] myData; } RestAssured setup required for decoding to fail byte [] data = "My data" .getBytes(StandardCharsets.UTF_8); String base64data = Base64.getEncoder().encodeToString(data); MultiPartSpecification multipart = new MultiPartSpecBuilder(base64data) .header( "Content-Transfer-Encoding" , "base64" ) .header( "Transfer-Encoding" , "base64" ) .controlName( "myData" ) .mimeType(MediaType.APPLICATION_OCTET_STREAM) .build(); Response response = given() .multiPart(multipart) .contentType(MediaType.MULTIPART_FORM_DATA) .log() .all( false ) .expect() .statusCode(HttpStatus.SC_OK) .contentType(MediaType.APPLICATION_JSON) .and() .log() .everything() .when() .post( "/dosomething" );