TIBQuery2.Assign(TIBQuery1) doesn't work

I am tryng to create a TIBQuery at runtime which must have the same
calculated fields as a TIBQuery I have already created at design time.
If I try to assign the design one to the runtime one, I get an error
at runtime saying cannot assign a TIBQuery to a TIBQuery. What am I
not uderstanding here?
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