i am trying to upload a file using spring web flow 2.0.2-RELEASE and I get the following error message:

Caused by: java.lang.IllegalArgumentException: Map key 'file' has value [org.springframework.web.multipart.commons.CommonsM ultipartFile] that is not of expected type class [java.lang.String], instead it is of type [org.springframework.web.multipart.commons.CommonsM ultipartFile]
at org.springframework.binding.collection.MapAccessor .assertKeyValueInstanceOf(MapAccessor.java:421)
at org.springframework.webflow.core.collection.LocalP arameterMap.get(LocalParameterMap.java:133)

it seems to be at binding time. any idea?

thanks in advance!!