Hello! I have library: mylib. And application: myapp. Library will use Cardinality package. So, I added to mylib's stack.yaml: ==added=== extra-deps: - https://hackage.haskell.org/package/Cardinality-0.2/Cardinality-0.2.tar.gz # Override default flag values for local packages and extra-deps flags: Cardinality: allow-never: true ===end-of-added=== and I added to mylib's cabal file: ===added=== build-depends: ... ... , Cardinality ===end-of-added=== Seems that it's compiling. OK, now I try to build myapp, which early was building without any problems (it depends on mylib). But I get error: ===error=== Cardinality must match -any, but the stack configuration has no specified version (latest matching version is 0.2) needed since mylib is a build target. Some potential ways to resolve this: * Recommended action: try adding the following to your extra-deps in /xxxxx/myapp/stack.yaml: - Cardinality-0.2 * Set 'allow-newer: true' to ignore all version constraints and build anyway. * You may also want to try using the 'stack solver' command. Plan construction failed. ===end-of-error=== So, what am I doing wrongly? Why stack want adding of the same things in myapp's stack.yaml which were already added in mylib's stack.yaml?! /Best regards, Paul