Am I overreacting for feeling hurt after a conversation with my fiancé?

My fiancé and I were talking about finances and future plans last night, and he brought up the idea of setting some things in writing before we get married basically a prenup. He said it’s just practical and that it protects both of us, but I honestly felt this weird wave of sadness when he mentioned it. I’ve always thought those things were for people who didn’t fully trust each other, and it caught me off guard. I didn’t argue or get mad, but I definitely shut down a bit. He told me I was overreacting and taking it too personally, but I don’t know… part of me feels like it changes the tone of what marriage is supposed to mean.
So, am I actually overreacting here or is it normal to feel a little off when someone you love brings up something like that?