Stored procedure / query needing additional field in 2% of all use-cases. Best practises?

I have a stored procedure used in aound 50 different places within a large application. One of these 50 contexts would require an additional field from this procedure.

I can think of two different approaches:

1. Update the stored procedure to return the missing field. That means that I will always request some additional data that will be useless in the 49 of 50 other use-cases.
2. Let the stored procedure as it is (withouth the needed additional data). And when I need the additional data (1 of 50 use-cases), query the base after the SP returns to enhance the SP result set into a dedicated DTO. In this case I would add this extra code into my business layer. That means extra code and getting all the data in two queries instead of one.

What would be the best practices?