Lookup column to Document Library shows no results

HI all,

I'm attempting to create a lookup column in a SharePoint list that references links in a SharePoint Document Library. I create the lookup column to reference the "Title" column of the item in the Document Library, and no values appear in the drop-down. However, when I switch the lookup column to reference the ID column, values appear. 

I've tried a variety of names and in the Name/Title field but I'm still getting blank results. I don't want to have to use another Single Line of Text column, either. Is this a known limitation or am I missing something?

Thanks!