Joe in the friend zone.

I have a friend who we'll call... Joe. Joe was a friend of mine during my first and second years of highschool until he graduated. Earlier this year Joe wanted to meet up again and hang out so we watched a few movies together. Joe is boring but otherwise a nice guy. Wednesday he asked me over facebook "How about dinner sometime next week. I will buy. Would you be interested in calling it a 'date'?"
I hate to friend zone my pal but there's a problem here. With me being an aromantic asexual I am just not willing to go that far. Pretty sure I told him about this so he probably forgot.
I still owe him money though because he purchased my movie ticket before (I didn't stand a chance, he already bought the thing by the time I got to the theater!) so I feel like I owe him. Maybe I should agree to dinner but scrap the "date" title and pay for his meal. But I really want him to know that I just don't want a boyfriend.
Would this be too conspicuous?

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