Oh, I'm sorry for misunderstanding.

Why I added `include Liquid` was to prevent `uninitialized constant IncludeTagTest::CustomInclude::QuotedFragment (NameError)`.

As you mentioned, `include Liquid` may be a bad choce. Without `include Liquid`, `QuotedFragment` in line 196 should be substituted with `Liquid::QuotedFragment`. I have just [commited](https://github.com/zerobase/liquid/commit/70513fccaf159e322dabcbe84d8b96f86cb00081) the patch.

Hope this helps.