424 object required for reportitem object

why error appears: 424 object required for below code

Sub test()
Dim msg as Object

If TypeOf msg Is MailItem Then
MsgForMailItem (msg) ' here is OK
ElseIf TypeOf msg Is ReportItem Then
MsgForReportItem (msg) ' here error appears: 424 Object required
End If
End Sub

Function MsgForReportItem (ri as Object)
MsgBox "Report"
' ... another action
End Function

Function msgForMailItem (mi as Object)
MsgBox "Mail"
' ... another action
End Function

Where is the code that shows how you are using the "msg" variable before entering the If statement?