How do I make up for watching ahead in a series we were meant to finish together?

I watched the next episode while my partner was out. It ended on a big reveal, so I watched another. When he came home and suggested our usual episode, I admitted I'd gone ahead.

He wasn't upset about spoilers; I hadn't told him what happened. He said I'd taken a shared evening and turned it into something I'd already done. We'd been saving the series for nights together, though we hadn't made an explicit rule about it.

I offered to watch the episodes again with him. He said that wasn't quite the same as both of us finding out what happened. I understand, but I don't know what else would repair something this small. Do I simply apologise and keep the remaining episodes for us? I don't want to dismiss a ritual because it happens to involve a television show.