`explain()` plan fails with redshift database but works if a line in `backend-postgres.R` is removed

[rmcd1024]

I'm using dbplyr with redshift. The explain function fails with an error but works if I comment out a line in backend-postgres.R.

I construct a dplyr expression named (e.g.) dbquery and then explain(dbquery). The sql translation is printed but the plan is not. I consistently get the following error:

<PLAN>
Error: Failed to prepare query: ERROR:
LINE 1: EXPLAIN (FORMAT text) SELECT *
                 ^
syntax error at or near "FORMAT"

The function backend-postgres.R contains this code

  build_sql(
    "EXPLAIN ",
    (!is.null(format)) sql(paste0("(FORMAT ", format, ") ")),
    sql,
    con = con
  )

If I comment out the line beginning (!is.null, the explain function works.

I apologize for not offering a reprex, but I don't have access to a public redshift database.