Sql error with backquotes, says there's a syntax error at or near "`"

I'm trying to load a database into Heroku from a sql file, however I get a syntax error from back quotes / backticks.

heroku pg:psql < backup.sql

Outputs this error:

syntax error at or near "`"

Why is that? Aren't backquotes valid?

I can find/replace them with something else if that would be good to try.