Compilation of directory package on GHC 7.4

Dear maintainers, The directory package is currently not compiling on GHC 7.4, leading to a compile failure of packages that depend on it. Hackage has a build failure log for GHC 7.4. I propose the attached patch, although I have not tested it on GHC 7.6. Can this (or an alternative fix) please be considered? Thanks in advance, Dominique Devriese