Some flags set using :seti seem to be ignored

Some flags, when set using :seti instead of :set, seem to be ignored:

ghci> :type id
id :: a -> a

ghci> :seti -fprint-explicit-foralls
ghci> :type id
id :: a -> a

ghci> :set -fprint-explicit-foralls
ghci> :type id
id :: forall {a}. a -> a

It seems that :seti -fprint-explicit-foralls does not do anything. The user's guide seems to indicate this should work:

GHCi actually maintains two sets of options:

• The loading options apply when loading modules
• The interactive options apply when evaluating expressions and commands typed at the GHCi prompt.

The :set command modifies both, but there is also a :seti command (for “set interactive”) that affects only the interactive options set.