Hi, I am using the parseTime function from Data.Time.Format. The first parameter is a TimeLocale defined in System.Locale (old-locale-1.0.0.2). I first wrote a trivial little module to test my understanding in ghci: module Tbasic where import Data.Time import System.Locale parseDate :: String -> Maybe UTCTime parseDate s = parseTime defaultTimeLocale "%d/%m/%Y" s Works fine. I then tried using this same function in my Snap web application. The application builds (via cabal install) fine. However when I start up the application and make my first request I get the following error: A web handler threw an exception. Details: Compile errors: Could not find module `System.Locale': It is a member of the hidden package `old-locale-1.0.0.2'. Use -v to see a list of the files searched for. I have added old-locale to Build-depends in the applications .cabal file. old-locale-1.0.0.2 appears in the global list of packages when I run ghc-pkg list Unsure what to try next. To be honest I don't understand a compile error at runtime given I didn't activate dynamic recompilation (i.e. I last built using cabal install, not cabal install -fdevelopment). appreciate any advice, Todd