GHCi panics when attempting to load archives

If I have the following module:

module Numeric.Integer ( is_prime_ats
                       ) where

import           Foreign.C

foreign import ccall is_prime_ats :: CInt -> CBool

and I attempt to open it in GHCi with the following

/opt/ghc/bin/ghci-8.4.2 -lnumbertheory -L../dist-newstyle/lib Numeric.Integer

(with a file libnumertheory.a in ../dist-newstyle/lib)

I get a panic and a request to open a bug report. I am guessing that at the least this supposed to be a different error message.

GHCi, version 8.4.1.20180329: http://www.haskell.org/ghc/  :? for help
ghc: panic! (the 'impossible' happened)
  (GHC version 8.4.1.20180329 for x86_64-unknown-linux):
    Loading archives not supported
Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug

If I instead place a shared library (i.e. libnumbertheory.so) in ../dist-newstyle/lib) then this does not panic.