Solange Knowles unexpectedly canceled her appearance at the Boston Calling festival so she can be present in the delivery room when her sister Beyonce delivers her twins over the holiday weekend.

The 30-year-old Cranes in the Sky singer blamed “production delays” for the abrupt cancelation that left her fans disappointed.

Maybe her fans would understand if they knew the real reason — that she’s clearing her schedule in anticipation of her nephews’ arrival.

“Unfortunately, Solange is unable to perform due to production delays and complications beyond her control,” organizers at the Harvard Athletic Complex in Boston wrote in a social media post late Thursday.

The singer addressed her angry fans on social media.

“I’m really really sorry/sad about this but I fought hard to only give u my best, & tons of production drama/delays got all up in the way,” she wrote on Friday.

She promised to make it up to her fans at a later date.

“I’m coming back though to do a one off show. Making it my mission. I will give it, and you my all.”

Rappers Migos were called on to replace Solange at the festival. The lineup includes headliners Chance the Rapper and Bon Iver, along with other local acts.

Photos by Backgrid, Getty Images