Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: ephemeral-0.0.1 (user goal) [__1] trying: numhask-0.7.1.0 (dependency of ephemeral) [__2] next goal: box-csv (dependency of ephemeral) [__2] rejecting: box-csv-0.0.3 (conflict: numhask==0.7.1.0, box-csv => numhask>=0.6 && <0.7) [__2] skipping: box-csv-0.0.2 (has the same characteristics that caused the previous version to fail: excludes 'numhask' version 0.7.1.0) [__2] trying: box-csv-0.0.1 [__3] next goal: box (dependency of ephemeral) [__3] rejecting: box-0.6.3 (conflict: box-csv => box>=0.4 && <0.6) [__3] skipping: box-0.6.2, box-0.6.1, box-0.6.0 (has the same characteristics that caused the previous version to fail: excluded by constraint '>=0.4 && <0.6' from 'box-csv') [__3] rejecting: box-0.5.0 (conflict: ephemeral => box>=0.6 && <0.7) [__3] skipping: box-0.4.0, box-0.3.0, box-0.2.0, box-0.1.0, box-0.0.1.5, box-0.0.1.4, box-0.0.1.2, box-0.0.1.1 (has the same characteristics that caused the previous version to fail: excluded by constraint '>=0.6 && <0.7' from 'ephemeral') [__3] fail (backjumping, conflict set: box, box-csv, ephemeral) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: ephemeral, numhask, box, box-csv Try running with --minimize-conflict-set to improve the error message.