diff --git a/bower.json b/bower.json
index ac1de63..b239b93 100644
--- a/bower.json
+++ b/bower.json
@@ -26,20 +26,22 @@
     "output"
   ],
   "dependencies": {
-    "purescript-arrays": "^3.0.0",
-    "purescript-either": "^2.0.0",
-    "purescript-foreign": "^3.0.0",
-    "purescript-foldable-traversable": "^2.0.0",
-    "purescript-transformers": "^2.0.0",
-    "purescript-aff": "^2.0.0",
-    "purescript-integers": "^2.0.0",
-    "purescript-datetime": "^2.0.0",
-    "purescript-unsafe-coerce": "^2.0.0",
-    "purescript-nullable": "^2.0.0"
+    "purescript-arrays": "^4.0.0",
+    "purescript-either": "^3.0.0",
+    "purescript-foreign": "^4.0.0",
+    "purescript-foldable-traversable": "^3.0.0",
+    "purescript-transformers": "^3.0.0",
+    "purescript-aff": "^3.0.0",
+    "purescript-integers": "^3.0.0",
+    "purescript-datetime": "^3.0.0",
+    "purescript-unsafe-coerce": "^3.0.0",
+    "purescript-nullable": "^3.0.0",
+    "purescript-prelude": "^3.0.0",
+    "purescript-foreign-generic": "^4.0.0"
   },
   "devDependencies": {
-    "purescript-spec": "^0.10.0",
-    "purescript-generics": "^3.0.0",
-    "purescript-js-date": "^3.0.0"
+    "purescript-spec": "^1.0.0",
+    "purescript-generics": "^4.0.0",
+    "purescript-js-date": "^4.0.0"
   }
 }
diff --git a/src/Database/Postgres.purs b/src/Database/Postgres.purs
index 84a6560..b6642d0 100644
--- a/src/Database/Postgres.purs
+++ b/src/Database/Postgres.purs
@@ -17,12 +17,12 @@ module Database.Postgres
   ) where
 
 import Prelude
-import Control.Monad.Eff (Eff)
+import Control.Monad.Eff (kind Effect, Eff)
 import Data.Either (Either, either)
 import Data.Function.Uncurried (Fn2(), runFn2)
 import Data.Array ((!!))
 import Data.Foreign (Foreign, MultipleErrors)
-import Data.Foreign.Class (class IsForeign, read)
+import Data.Foreign.Class (class Decode, decode)
 import Data.Maybe (Maybe(Just, Nothing), maybe)
 import Control.Monad.Except (runExcept)
 import Control.Monad.Aff (Aff, finally)
@@ -35,9 +35,9 @@ import Database.Postgres.SqlValue (SqlValue)
 
 newtype Query a = Query String
 
-foreign import data Client :: *
+foreign import data Client :: Type
 
-foreign import data DB :: !
+foreign import data DB :: Effect
 
 type ConnectionString = String
 
@@ -72,45 +72,45 @@ execute_ (Query sql) client = void $ runQuery_ sql client
 
 -- | Runs a query and returns all results.
 query :: forall eff a
-  . (IsForeign a)
+  . (Decode a)
   => Query a -> Array SqlValue -> Client -> Aff (db :: DB | eff) (Array a)
 query (Query sql) params client = do
   rows <- runQuery sql params client
-  either liftError pure (runExcept (sequence $ read <$> rows))
+  either liftError pure (runExcept (sequence $ decode <$> rows))
 
 -- | Just like `query` but does not make any param replacement
-query_ :: forall eff a. (IsForeign a) => Query a -> Client -> Aff (db :: DB | eff) (Array a)
+query_ :: forall eff a. (Decode a) => Query a -> Client -> Aff (db :: DB | eff) (Array a)
 query_ (Query sql) client = do
   rows <- runQuery_ sql client
-  either liftError pure (runExcept (sequence $ read <$> rows))
+  either liftError pure (runExcept (sequence $ decode <$> rows))
 
 -- | Runs a query and returns the first row, if any
 queryOne :: forall eff a
-  . (IsForeign a)
+  . (Decode a)
   => Query a -> Array SqlValue -> Client -> Aff (db :: DB | eff) (Maybe a)
 queryOne (Query sql) params client = do
   rows <- runQuery sql params client
-  maybe (pure Nothing) (either liftError (pure <<< Just)) (readFirst rows)
+  maybe (pure Nothing) (either liftError (pure <<< Just)) (decodeFirst rows)
 
 -- | Just like `queryOne` but does not make any param replacement
-queryOne_ :: forall eff a. (IsForeign a) => Query a -> Client -> Aff (db :: DB | eff) (Maybe a)
+queryOne_ :: forall eff a. (Decode a) => Query a -> Client -> Aff (db :: DB | eff) (Maybe a)
 queryOne_ (Query sql) client = do
   rows <- runQuery_ sql client
-  maybe (pure Nothing) (either liftError (pure <<< Just)) (readFirst rows)
+  maybe (pure Nothing) (either liftError (pure <<< Just)) (decodeFirst rows)
 
 -- | Runs a query and returns a single value, if any.
 queryValue :: forall eff a
-  . (IsForeign a)
+  . (Decode a)
   => Query a -> Array SqlValue -> Client -> Aff (db :: DB | eff) (Maybe a)
 queryValue (Query sql) params client = do
   val <- runQueryValue sql params client
-  pure $ either (const Nothing) Just (runExcept (read val))
+  pure $ either (const Nothing) Just (runExcept (decode val))
 
 -- | Just like `queryValue` but does not make any param replacement
-queryValue_ :: forall eff a. (IsForeign a) => Query a -> Client -> Aff (db :: DB | eff) (Maybe a)
+queryValue_ :: forall eff a. (Decode a) => Query a -> Client -> Aff (db :: DB | eff) (Maybe a)
 queryValue_ (Query sql) client = do
   val <- runQueryValue_ sql client
-  either liftError (pure <<< Just) $ runExcept (read val)
+  either liftError (pure <<< Just) $ runExcept (decode val)
 
 -- | Connects to the database, calls the provided function with the client
 -- | and returns the results.
@@ -130,8 +130,8 @@ withClient :: forall eff a
   -> Aff (db :: DB | eff) a
 withClient info p = runFn2 _withClient (mkConnectionString info) p
 
-readFirst :: forall a. IsForeign a => Array Foreign -> Maybe (Either MultipleErrors a)
-readFirst rows = runExcept <<< read <$> (rows !! 0)
+decodeFirst :: forall a. Decode a => Array Foreign -> Maybe (Either MultipleErrors a)
+decodeFirst rows = runExcept <<< decode <$> (rows !! 0)
 
 liftError :: forall e a. MultipleErrors -> Aff e a
 liftError errs = throwError $ error (show errs)
diff --git a/src/Database/Postgres/SqlValue.purs b/src/Database/Postgres/SqlValue.purs
index 301eda8..1292b68 100644
--- a/src/Database/Postgres/SqlValue.purs
+++ b/src/Database/Postgres/SqlValue.purs
@@ -14,7 +14,7 @@ import Data.Time (hour, minute, second)
 import Unsafe.Coerce (unsafeCoerce)
 import Data.Nullable (toNullable)
 
-foreign import data SqlValue :: *
+foreign import data SqlValue :: Type
 
 class IsSqlValue a where
   toSql :: a -> SqlValue
diff --git a/test/Main.purs b/test/Main.purs
index 4d3565a..89bbc6b 100644
--- a/test/Main.purs
+++ b/test/Main.purs
@@ -1,35 +1,37 @@
 module Test.Main where
 
 import Prelude
+
 import Control.Monad.Aff (Aff, apathize, attempt)
+import Control.Monad.Aff.AVar (AVAR)
 import Control.Monad.Eff (Eff)
 import Control.Monad.Eff.Class (liftEff)
 import Control.Monad.Eff.Console (CONSOLE)
 import Control.Monad.Eff.Exception (error)
+import Control.Monad.Eff.Timer (TIMER)
 import Control.Monad.Error.Class (throwError)
 import Data.Array (length)
 import Data.Date (canonicalDate)
-import Data.DateTime (DateTime(..))
 import Data.Date.Component (Month(..))
-import Data.Enum (toEnum)
-import Data.Time (Time(..))
+import Data.DateTime (DateTime(..))
 import Data.Either (either)
+import Data.Enum (toEnum)
 import Data.Foreign (Foreign)
+import Data.Foreign.Class (class Decode, decode)
+import Data.Foreign.Index (readProp)
+import Data.Generic (class Generic, gEq)
 import Data.JSDate (toDateTime)
 import Data.Maybe (Maybe(Nothing, Just), maybe)
-import Data.Foreign.Class (class IsForeign, readProp)
-import Data.Generic (class Generic, gEq)
-import Database.Postgres (DB, Query(Query), queryOne_, execute, execute_, withConnection, query, withClient, end, query_, connect, queryValue_, mkConnectionString)
+import Data.Time (Time(..))
+import Database.Postgres (DB, Query(Query), connect, end, execute, execute_, mkConnectionString, query, queryOne_, queryValue_, query_, withClient, withConnection)
 import Database.Postgres.SqlValue (toSql)
 import Database.Postgres.Transaction (withTransaction)
 import Node.Process (PROCESS)
-
-import Unsafe.Coerce (unsafeCoerce)
-
 import Test.Spec (describe, it)
-import Test.Spec.Runner (run)
 import Test.Spec.Assertions (fail, shouldEqual)
 import Test.Spec.Reporter.Console (consoleReporter)
+import Test.Spec.Runner (run)
+import Unsafe.Coerce (unsafeCoerce)
 
 data Artist = Artist
   { name :: String
@@ -45,7 +47,16 @@ connectionInfo =
   , password: "test"
   }
 
-main :: Eff (process :: PROCESS, console :: CONSOLE , db :: DB) Unit
+main :: forall eff.
+  Eff
+    ( console :: CONSOLE
+    , timer :: TIMER
+    , avar :: AVAR
+    , process :: PROCESS
+    , db :: DB
+    | eff
+    )
+    Unit
 main = run [consoleReporter] do
   describe "connection string" do
     it "should build one from the connection record" do
@@ -111,7 +122,7 @@ main = run [consoleReporter] do
         ) dt
 
 
-  describe "transactions" do 
+  describe "transactions" do
     it "does not commit after an error inside a transation" do
       withConnection connectionInfo $ \c -> do
         execute_ (Query "delete from artist") c
@@ -138,8 +149,8 @@ derive instance genericArtist :: Generic Artist
 instance eqArtist :: Eq Artist where
   eq = gEq
 
-instance artistIsForeign :: IsForeign Artist where
-  read obj = do
-    n <- readProp "name" obj
-    y <- readProp "year" obj
+instance artistIsForeign :: Decode Artist where
+  decode obj = do
+    n <- decode =<< readProp "name" obj
+    y <- decode =<< readProp "year" obj
     pure $ Artist { name: n, year: y }