Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: nested-routes-9.0.1.1 (user goal) [__1] trying: tries-0.0.5 (dependency of nested-routes) [__2] trying: bytestring-trie-0.2.4.1 (dependency of tries) [__3] next goal: base (dependency of nested-routes) [__3] rejecting: base-4.11.1.0/installed-4.1... (conflict: bytestring-trie +/-applicativeinbase +/-base4 +/-bytestringinbase => base<2.2 || >=3 && <4.11) [__3] rejecting: base-4.11.1.0, base-4.11.0.0, base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: nested-routes, base, bytestring-trie, tries