Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: genvalidity-aeson-0.2.0.0 (user goal) [__1] trying: validity-aeson-0.2.0.0 (dependency of genvalidity-aeson) [__2] trying: validity-vector-0.1.0.0 (dependency of validity-aeson) [__3] next goal: validity (dependency of genvalidity-aeson) [__3] rejecting: validity-0.5.0.0 (conflict: validity-vector => validity>=0.4 && <0.5) [__3] rejecting: validity-0.4.0.4, validity-0.4.0.3, validity-0.4.0.2, validity-0.4.0.1, validity-0.4.0.0, validity-0.3.3.0, validity-0.3.2.0, validity-0.3.1.1, validity-0.3.0.4, validity-0.3.0.3, validity-0.3.0.2, validity-0.3.0.1, validity-0.3.0.0, validity-0.2.0.0, validity-0.1.0.0 (conflict: genvalidity-aeson => validity>=0.5 && <0.6) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: genvalidity-aeson, validity, validity-aeson, validity-vector