PostgreSQL: Create Index Failing

Here’s the offending code:

CREATE INDEX auth_user_username_6821ab7c_like
  ON public.auth_user
  USING btree (username varchar_pattern_ops);

The error I received:

Expected ")", ",", "ASC", "COLLATE", "DESC", or "NULLS" but "v" found.

According to the importer, the varchar_pattern_ops is the problem. I looked it up in PostgreSQL documentation and found that varchar_pattern_ops is an operator class.

I stripped all occurrences out so I could complete the import, but shouldn’t operator classes be preserved for future exports? Is there a better way to format this to work with DBML?