Pension RMD after death

My husband died 4 years ago.  He had received a small monthly pension from a former employer.  Out of the blue, this year I received a check in the mail.  The 1099R I received says in box 7 (4) which is Death.  I had heard nothing from them after I let them know he had died.  on TurboTax, it asks if this was a RMD and that one was due.  He was born in 1937, i was born in 1948.  I have figured the RMD on my money but not this one.  Do i need to pay on this.  He had opted to receive monthly payments with them to not continue after he died.