Incorrect module name in .bkp instantiation causes a "Failed to load interface" error

When attempting to compile the following .bkp file:

unit basic where
  signature Basic where

unit mod where
  module Mod where

unit main where
  dependency basic
    [ Basic = mod:Nonsense ]

GHC produces the error:

ghc --backpack Error2.bkp
[1 of 3] Processing basic
[2 of 3] Processing mod
  Instantiating mod
  [1 of 1] Compiling Mod              ( mod\Mod.hs, mod\Mod.o )
[3 of 3] Processing main
  Instantiating main
  [1 of 1] Including basic[Basic=mod:Nonsense]
    Instantiating basic[Basic=mod:Nonsense]
    [1 of 1] Compiling Basic[sig]       ( basic\Basic.hsig, basic\basic-ER8okxhuIcsFJ32OYv1Qcp\Basic.o )

<no location info>: error:
    Failed to load interface for `Nonsense'
There are files missing in the `mod' package,
try running 'ghc-pkg check'.
Use -v (or `:set -v` in ghci) to see a list of the files searched for.

It would be better to catch this problem earlier on, and report a proper error message.