Error setting field values with Set-TfsWorkItem

[igoravl]

When invoking Set-TfsWorkItem with -Fields argument, it throws an exception:

PS > Set-TfsWorkItem 1 -Fields @{'System.AreaPath' = 'foo'; 'System.IterationPath' = 'bar'}
Set-TfsWorkItem : Unable to cast object of type 'System.Collections.Hashtable' to type 'System.String[]'.
At line:1 char:1
+ Set-TfsWorkItem 1 -Fields @{'System.AreaPath' = 'foo...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Set-TfsWorkItem], InvalidCastException
    + FullyQualifiedErrorId : System.InvalidCastException,TfsCmdlets.Cmdlets.WorkItem.SetWorkItem