[Haskell-beginners] Conflict with global lib from sandbox

Hi, called "cabal sandbox init" from inside an empty directory. When running cabal install... see errors like that: /home/my-name/.cabal/lib/i386-linux-ghc-7.6.3/unix-2.7.2.2/libHSunix-2.7.2.2.a(HsUnix.o):(.text+0x20): first defined here /usr/lib/ghc/unix-2.6.0.1/libHSunix-2.6.0.1.a(HsUnix.o): In function `__hsunix_grantpt': Shouldn't /usr/lib/... be hidden from inside a sandbox? Thanks, Andreas