SAP Message 7A150 - Reference field & invalid, correct entry

Diagnosis
Field "&V1&" can not be used as a reference field. Only fields with thetype "percentage of completion" (planned or actual) may be used as areference field. A field cannot refer to itself.

System Response
INCLUDE 'NA_ALLG_NOFUNKTION' OBJECT DOKU ID TX

Procedure
Enter a different reference field for &V1&.