diff --git a/Setup.hs b/Setup.hs
--- a/Setup.hs
+++ b/Setup.hs
@@ -16,7 +16,7 @@
 maybeInstallActions :: ConfigFlags -> IO ()
 maybeInstallActions cfs = bool nothing act cond
     where act = installActions
-          nothing = pure mempty
+          nothing = mempty
           cond = (mkFlagName "no-executable", True) `notElem` unFlagAssignment (configConfigurationsFlags cfs)
 
 main :: IO ()
diff --git a/app/Main.hs b/app/Main.hs
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -51,6 +51,7 @@
                    , _lint       :: Bool
                    }
              | Check { _filePath :: String, _details :: Bool }
+             | CheckSet { _filePath :: String, _details :: Bool }
              | List
 
 userCmd :: Parser Command
@@ -64,7 +65,8 @@
     <> command "upgrade" (info (pure Upgrade) (progDesc "Upgrade to the latest version of atspkg"))
     <> command "valgrind" (info valgrind (progDesc "Run generated binaries through valgrind"))
     <> command "run" (info run' (progDesc "Run generated binaries"))
-    <> command "check" (info check' (progDesc "Audit a package set to ensure it is well-typed."))
+    <> command "check" (info check' (progDesc "Check that a pkg.dhall file is well-typed."))
+    <> command "check-set" (info checkSet (progDesc "Audit a package set to ensure it is well-typed."))
     <> command "list" (info (pure List) (progDesc "List available packages"))
     )
 
@@ -85,10 +87,18 @@
 install = Install
     <$> triple
 
+checkSet :: Parser Command
+checkSet = CheckSet
+    <$> targetP dhallCompletions id "check"
+    <*> details
+
 check' :: Parser Command
 check' = Check
-    <$> targetP dhallCompletions id "check"
-    <*> switch
+    <$> targetP dhallCompletions id "check-set"
+    <*> details
+
+details :: Parser Bool
+details = switch
     (long "detailed"
     <> short 'd'
     <> help "Enable detailed error messages")
@@ -190,7 +200,8 @@
 
 run :: Command -> IO ()
 run List                          = displayList "https://raw.githubusercontent.com/vmchale/atspkg/master/ats-pkg/pkgs/pkg-set.dhall"
-run (Check p b)                   = print =<< checkPkg p b
+run (Check p b)                   = print . ($ Version [0,1,0]) =<< checkPkg p b
+run (CheckSet p b)                = print =<< checkPkgSet p b
 run Upgrade                       = upgradeBin "vmchale" "atspkg"
 run Nuke                          = cleanAll
 run (Fetch u)                     = fetchPkg u
diff --git a/ats-pkg.cabal b/ats-pkg.cabal
--- a/ats-pkg.cabal
+++ b/ats-pkg.cabal
@@ -1,6 +1,6 @@
 cabal-version: 1.18
 name: ats-pkg
-version: 2.7.1.2
+version: 2.8.0.0
 license: BSD3
 license-file: LICENSE
 copyright: Copyright: (c) 2018 Vanessa McHale
@@ -65,13 +65,13 @@
     ghc-options: -Wall -Wincomplete-uni-patterns
                  -Wincomplete-record-updates -Wcompat
     build-depends:
-        base >=4.7 && <5,
+        base >=4.11 && <5,
         http-client -any,
         bytestring -any,
         file-embed -any,
         shake -any,
         bzlib -any,
-        Cabal >=2.0.0.0,
+        Cabal >=2.2.0.0,
         lzma -any,
         tar -any,
         zlib -any,
@@ -86,7 +86,7 @@
         microlens -any,
         microlens-th -any,
         mtl -any,
-        dhall >=1.10.0,
+        dhall >=1.12.0,
         ansi-wl-pprint -any,
         shake-ats >=1.3.0.0,
         shake-ext >=2.6.0.0,
diff --git a/dhall/atslib.dhall b/dhall/atslib.dhall
--- a/dhall/atslib.dhall
+++ b/dhall/atslib.dhall
@@ -37,10 +37,10 @@
 {- ATSPackage parts -}
 let prelude = https://raw.githubusercontent.com/vmchale/atspkg/master/ats-pkg/dhall/atspkg-prelude.dhall
 
-in prelude.default //
+in prelude.default ⫽
   { libraries =
     [
-      prelude.staticLib //
+      prelude.staticLib ⫽
       { libTarget = "target/lib/libatslib.a"
       , name = "atslib"
       , src =
@@ -51,7 +51,7 @@
           ]
       , includes = ([] : List Text)
       }
-    , prelude.staticLib //
+    , prelude.staticLib ⫽
       { libTarget = "target/lib/libatsopt.a"
       , name = "atsopt"
       , src = mapUtil [ "main", "print", "util" ]
diff --git a/src/Distribution/ATS.hs b/src/Distribution/ATS.hs
--- a/src/Distribution/ATS.hs
+++ b/src/Distribution/ATS.hs
@@ -43,7 +43,7 @@
 maybeCleanBuild li =
     let cf = configConfigurationsFlags (configFlags li) in
 
-    unless ((mkFlagName "development", True) `elem` cf) $
+    unless ((mkFlagName "development", True) `elem` unFlagAssignment cf) $
         putStrLn "Cleaning up ATS dependencies..." >>
         cleanATSCabal
 
@@ -83,7 +83,7 @@
     bool act nothing cond
     where act = (>> stopGlobalPool) . parallel_ . fmap fetchDependency
           nothing = pure mempty
-          cond = (mkFlagName "with-atsdeps", False) `elem` configConfigurationsFlags cfs
+          cond = (mkFlagName "with-atsdeps", False) `elem` unFlagAssignment (configConfigurationsFlags cfs)
 
 fetchDependency :: ATSDependency -> IO ()
 fetchDependency (ATSDependency libNameATS dirName url) = do
diff --git a/src/Language/ATS/Package.hs b/src/Language/ATS/Package.hs
--- a/src/Language/ATS/Package.hs
+++ b/src/Language/ATS/Package.hs
@@ -3,6 +3,8 @@
                             , mkPkg
                             , cleanAll
                             , buildHelper
+                            -- * Dhall verification helpers
+                            , checkPkgSet
                             , checkPkg
                             -- * Ecosystem functionality
                             , displayList
diff --git a/src/Language/ATS/Package/Dhall.hs b/src/Language/ATS/Package/Dhall.hs
--- a/src/Language/ATS/Package/Dhall.hs
+++ b/src/Language/ATS/Package/Dhall.hs
@@ -1,13 +1,27 @@
-module Language.ATS.Package.Dhall ( checkPkg
+module Language.ATS.Package.Dhall ( checkPkgSet
+                                  , checkPkg
                                   ) where
 
+import           Data.Dependency
 import           Language.ATS.Package.PackageSet
+import           Language.ATS.Package.Type
 import           Quaalude
 
-checkPkg :: FilePath -- ^ Path to @.dhall@ file defining a package set.
-         -> Bool -- ^ Whether to print detailed error messages.
-         -> IO ATSPackageSet
-checkPkg path d = do
+checkPkg :: FilePath
+         -> Bool
+         -> IO (Version -> ATSDependency)
+checkPkg = checkDhall
+
+checkDhall :: Interpret a
+      => FilePath
+      -> Bool
+      -> IO a
+checkDhall path d = do
     x <- input auto (pack ('.' : '/' : path))
     let f = bool id detailed d
-    f (pure (x :: ATSPackageSet))
+    f (pure x)
+
+checkPkgSet :: FilePath -- ^ Path to @.dhall@ file defining a package set.
+            -> Bool -- ^ Whether to print detailed error messages.
+            -> IO ATSPackageSet
+checkPkgSet = checkDhall
diff --git a/src/Language/ATS/Package/Type.hs b/src/Language/ATS/Package/Type.hs
--- a/src/Language/ATS/Package/Type.hs
+++ b/src/Language/ATS/Package/Type.hs
@@ -37,6 +37,7 @@
                                    }
                 deriving (Eq, Show, Generic, Binary, Interpret, Hashable)
 
+deriving newtype instance Inject Version
 deriving newtype instance Interpret Version
 deriving newtype instance Hashable Version
 
diff --git a/src/Quaalude.hs b/src/Quaalude.hs
--- a/src/Quaalude.hs
+++ b/src/Quaalude.hs
@@ -18,7 +18,6 @@
                 , isSuffixOf
                 , on
                 , both
-                , (<>)
                 , (***)
                 , (&&&)
                 , (<=<)
@@ -42,6 +41,7 @@
                 , thread
                 -- * Dhall reëxports
                 , Interpret
+                , Inject
                 , Generic
                 , Binary
                 , input
@@ -122,7 +122,6 @@
 import           Data.Foldable
 import           Data.List
 import           Data.Maybe                   (fromMaybe)
-import           Data.Semigroup
 import           Data.Text.Lazy               (pack, unpack)
 import           Data.Version                 (showVersion)
 import           Development.Shake            hiding (getEnv)