diff --git a/hasql.cabal b/hasql.cabal
--- a/hasql.cabal
+++ b/hasql.cabal
@@ -1,7 +1,7 @@
 name:
   hasql
 version:
-  0.19.3.3
+  0.19.4
 category:
   Hasql, Database, PostgreSQL
 synopsis:
@@ -74,7 +74,7 @@
     -- parsing:
     attoparsec >= 0.10 && < 0.14,
     -- database:
-    postgresql-binary >= 0.7.3 && < 0.8,
+    postgresql-binary >= 0.7.4 && < 0.8,
     postgresql-libpq == 0.9.*,
     -- data:
     dlist >= 0.7 && < 0.8,
diff --git a/library/Hasql/Decoders.hs b/library/Hasql/Decoders.hs
--- a/library/Hasql/Decoders.hs
+++ b/library/Hasql/Decoders.hs
@@ -42,6 +42,7 @@
   composite,
   hstore,
   enum,
+  custom,
   -- * Array
   Array,
   arrayDimension,
@@ -418,6 +419,14 @@
 json :: Value Aeson.Value
 json =
   Value (Value.decoder (const Decoder.json))
+
+-- |
+-- Lifts a custom value decoder function to a 'Value' decoder.
+-- 
+{-# INLINABLE custom #-}
+custom :: (Bool -> ByteString -> Either Text a) -> Value a
+custom fn =
+  Value (Value.decoderFn fn)
 
 
 -- ** Composite value decoders
diff --git a/library/Hasql/Decoders/Value.hs b/library/Hasql/Decoders/Value.hs
--- a/library/Hasql/Decoders/Value.hs
+++ b/library/Hasql/Decoders/Value.hs
@@ -21,3 +21,8 @@
   {-# SCC "decoder" #-} 
   Value . ReaderT
 
+{-# INLINE decoderFn #-}
+decoderFn :: (Bool -> ByteString -> Either Text a) -> Value a
+decoderFn fn =
+  Value $ ReaderT $ \integerDatetimes -> Decoder.fn $ fn integerDatetimes
+