diff --git a/selda-postgresql.cabal b/selda-postgresql.cabal
--- a/selda-postgresql.cabal
+++ b/selda-postgresql.cabal
@@ -1,5 +1,5 @@
 name:                selda-postgresql
-version:             0.1.2.2
+version:             0.1.3.0
 synopsis:            PostgreSQL backend for the Selda database EDSL.
 description:         PostgreSQL backend for the Selda database EDSL.
                      Requires the PostgreSQL @libpq@ development libraries to be
@@ -20,6 +20,8 @@
 library
   exposed-modules:
     Database.Selda.PostgreSQL
+  other-modules:
+    Database.Selda.PostgreSQL.Encoding
   other-extensions:
     GADTs
     RecordWildCards
@@ -28,7 +30,7 @@
   build-depends:
       base             >=4.8     && <5
     , exceptions       >=0.8     && <0.9
-    , selda            >=0.1.4.1 && <0.2
+    , selda            >=0.1.5.0 && <0.2
     , text             >=1.0     && <1.3
   if !flag(haste)
     build-depends:
diff --git a/src/Database/Selda/PostgreSQL.hs b/src/Database/Selda/PostgreSQL.hs
--- a/src/Database/Selda/PostgreSQL.hs
+++ b/src/Database/Selda/PostgreSQL.hs
@@ -13,6 +13,7 @@
 import Control.Monad.Catch
 
 #ifndef __HASTE__
+import Database.Selda.PostgreSQL.Encoding
 import Database.PostgreSQL.LibPQ hiding (user, pass, db, host)
 import qualified Data.ByteString.Char8 as BS
 #endif
@@ -136,7 +137,7 @@
     q' | return_lastid = q <> " RETURNING LASTVAL();"
        | otherwise     = q
 
-    getLastId res = (read . BS.unpack . maybe "" id) <$> getvalue res 0 0
+    getLastId res = (readInt . maybe "0" id) <$> getvalue res 0 0
 
     getRows res = do
       rows <- ntuples res
@@ -146,7 +147,7 @@
       result <- mapM (getRow res types cols) [0..rows-1]
       pure $ case affected of
         Just "" -> (0, result)
-        Just s  -> (read $ BS.unpack s, result)
+        Just s  -> (readInt s, result)
         _       -> (0, result)
 
     getRow res types cols row = do
@@ -158,35 +159,6 @@
         Just val -> pure $ toSqlValue t val
         _        -> pure SqlNull
 
--- | Convert the given postgres return value and type to an @SqlValue@.
---   TODO: use binary format instead of text.
-toSqlValue :: Oid -> BS.ByteString -> SqlValue
-toSqlValue t val
-  | t == boolType    = SqlBool $ readBool val
-  | t == intType     = SqlInt $ read (BS.unpack val)
-  | t == doubleType  = SqlFloat $ read (BS.unpack val)
-  | t `elem` textish = SqlString (decodeUtf8 val)
-  | otherwise        = error $ "BUG: result with unknown type oid: " ++ show t
-  where
-    textish = [textType, timestampType, timeType, dateType]
-    readBool "f"   = False
-    readBool "0"   = False
-    readBool "0.0" = False
-    readBool "F"   = False
-    readBool _     = True
-
--- | Convert a parameter into an postgres parameter triple.
-fromSqlValue :: Lit a -> Maybe (Oid, BS.ByteString, Format)
-fromSqlValue (LitB b)    = Just (boolType, if b then "true" else "false", Text)
-fromSqlValue (LitI n)    = Just (intType, BS.pack $ show n, Text)
-fromSqlValue (LitD f)    = Just (doubleType, BS.pack $ show f, Text)
-fromSqlValue (LitS s)    = Just (textType, encodeUtf8 s, Text)
-fromSqlValue (LitTS s)   = Just (timestampType, encodeUtf8 s, Text)
-fromSqlValue (LitTime s) = Just (timeType, encodeUtf8 s, Text)
-fromSqlValue (LitDate s) = Just (dateType, encodeUtf8 s, Text)
-fromSqlValue (LitNull)   = Nothing
-fromSqlValue (LitJust x) = fromSqlValue x
-
 -- | Custom column types for postgres: auto-incrementing primary keys need to
 --   be @BIGSERIAL@, and ints need to be @INT8@.
 pgColType :: T.Text -> [ColAttr] -> Maybe T.Text
@@ -201,14 +173,4 @@
     Just $ T.unwords ("TIMESTAMP" : map compileColAttr attrs)
 pgColType _ _ =
     Nothing
-
--- | OIDs for all types used by Selda.
-boolType, intType, textType, doubleType, dateType, timeType, timestampType :: Oid
-boolType      = Oid 16
-intType       = Oid 20
-textType      = Oid 25
-doubleType    = Oid 701
-dateType      = Oid 1082
-timeType      = Oid 1083
-timestampType = Oid 1114
 #endif
diff --git a/src/Database/Selda/PostgreSQL/Encoding.hs b/src/Database/Selda/PostgreSQL/Encoding.hs
new file mode 100644
--- /dev/null
+++ b/src/Database/Selda/PostgreSQL/Encoding.hs
@@ -0,0 +1,81 @@
+{-# LANGUAGE GADTs, BangPatterns, OverloadedStrings #-}
+-- | Encoding/decoding for PostgreSQL.
+module Database.Selda.PostgreSQL.Encoding
+  ( toSqlValue, fromSqlValue
+  , readInt
+  ) where
+import qualified Data.ByteString as BS
+import Data.ByteString.Builder
+import Data.ByteString.Char8 (unpack)
+import qualified Data.ByteString.Lazy as LBS
+import Data.Text.Encoding
+import Database.PostgreSQL.LibPQ (Oid (..), Format (..))
+import Database.Selda.Backend (Lit (..), SqlValue (..))
+import Unsafe.Coerce
+
+-- | OIDs for all types used by Selda.
+boolType, intType, textType, doubleType, dateType, timeType, timestampType :: Oid
+boolType      = Oid 16
+intType       = Oid 20
+textType      = Oid 25
+doubleType    = Oid 701
+dateType      = Oid 1082
+timeType      = Oid 1083
+timestampType = Oid 1114
+
+-- | Convert a parameter into an postgres parameter triple.
+fromSqlValue :: Lit a -> Maybe (Oid, BS.ByteString, Format)
+fromSqlValue (LBool b)     = Just (boolType, toBS $ if b then word8 1 else word8 0, Binary)
+fromSqlValue (LInt n)      = Just (intType, toBS $ int64BE (fromIntegral n), Binary)
+fromSqlValue (LDouble f)   = Just (doubleType, toBS $ int64BE (unsafeCoerce f), Binary)
+fromSqlValue (LText s)     = Just (textType, encodeUtf8 s, Text)
+fromSqlValue (LDateTime s) = Just (timestampType, encodeUtf8 s, Text)
+fromSqlValue (LTime s)     = Just (timeType, encodeUtf8 s, Text)
+fromSqlValue (LDate s)     = Just (dateType, encodeUtf8 s, Text)
+fromSqlValue (LNull)       = Nothing
+fromSqlValue (LJust x)     = fromSqlValue x
+
+-- | Convert the given postgres return value and type to an @SqlValue@.
+toSqlValue :: Oid -> BS.ByteString -> SqlValue
+toSqlValue t val
+  | t == boolType    = SqlBool $ readBool val
+  | t == intType     = SqlInt $ readInt val
+  | t == doubleType  = SqlFloat $ read (unpack val)
+  | t `elem` textish = SqlString (decodeUtf8 val)
+  | otherwise        = error $ "BUG: result with unknown type oid: " ++ show t
+  where
+    textish = [textType, timestampType, timeType, dateType]
+    readBool "f"     = False
+    readBool "0"     = False
+    readBool "false" = False
+    readBool "n"     = False
+    readBool "no"    = False
+    readBool "off"   = False
+    readBool _       = True
+
+-- | Read an integer from a strict bytestring.
+--   Assumes that the bytestring does, in fact, contain an integer.
+readInt :: BS.ByteString -> Int
+readInt s
+  | BS.head s == asciiDash = negate $! go 1 0
+  | otherwise              = go 0 0
+  where
+    !len = BS.length s
+    !asciiZero = 48
+    !asciiDash = 45
+    go !i !acc
+      | len > i   = go (i+1) (acc * 10 + fromIntegral (BS.index s i - asciiZero))
+      | otherwise = acc
+
+-- | Reify a builder to a strict bytestring.
+toBS :: Builder -> BS.ByteString
+toBS = unChunk . toLazyByteString
+
+-- | Convert a lazy bytestring to a strict one.
+--   Avoids the copying overhead of 'LBS.toStrict' when there's only a single
+--   chunk, which should always be the case when serializing single parameters.
+unChunk :: LBS.ByteString -> BS.ByteString
+unChunk bs =
+  case LBS.toChunks bs of
+    [bs'] -> bs'
+    bss   -> BS.concat bss