tasty-discover with stack run 0 tests

I've just moved from using cabal directly to stack, but I'm having some problems with the test-suite. The library and executable works fine but stack test gives me

hml-0.1.0.0: test (suite: HML-test) 
All 0 tests passed (0.00s)

I.e. no tests were run. When I run the tests with cabal directly they work fine. I'm using tasty with tasty-discover. In hml.cabal the suite looks like this:

test-suite HML-test
  main-is:             Driver.hs
  hs-source-dirs:      test
  default-language:    Haskell2010
  ghc-options:         -Wall
  other-modules:       HML.Types.Test.PosInt
                       (...etc...)
  build-depends:       base >= 4.9
                       (... etc...)

The driver test/Driver.hs for tasty-discover looks like this:

{-# OPTIONS_GHC -F -pgmF tasty-discover -optF --tree-display #-}

Any ideas?