Size up or down if you're between Burton bindings?

Noob here. I bought Burton Mint Boa boots in womens 8.5 and am looking to order Burton Citizen strap bindings to go with them. The size chart on Burton’s website says size M for sizes 6-8 and L for 8+. At 8.5 is it better to size down a half size to the M or just buy the L?