Why is Seam fileUpload no longer working after upgrading to seam 2.1.x ?

Issue

• In some pages we are using the s:fileUpload Seam tag to upload files such as images, jar files. Data uploaded is bound to byte array that is a bean property: byte[] data.  After the upload is done the byte array is null instead of having a value. Note that this functionality in our side had been tested and worked when we were using Seam 2.0. So it seems this is a regression of seam.