building hashed-storage 0.4.3: Expected one of wanted constraints (BUG)

Using GHC 7.0.1-rc1 with the patch for trac#4345, while compiling Storage.Hashed.Monad from version 0.4.3 of the hashed-storage package I get the following message:

ghc: panic! (the 'impossible' happened)
  (GHC version 7.0.0 for i386-unknown-linux):
        Expected one of wanted constraints (BUG)

This is from http://hackage.haskell.org/package/hashed-storage-0.4.3. The bug still occurs using the latest version, 0.5.3.

Trac metadata

Trac field	Value
Version	7.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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building hashed-storage 0.4.3: Expected one of wanted constraints (BUG)