diff --git a/lib/Database/PostgreSQL/Opium/FromField.hs b/lib/Database/PostgreSQL/Opium/FromField.hs
index 30b21c9..d87270e 100644
--- a/lib/Database/PostgreSQL/Opium/FromField.hs
+++ b/lib/Database/PostgreSQL/Opium/FromField.hs
@@ -41,6 +41,9 @@ import qualified Database.PostgreSQL.Opium.Oid as Oid
 (\/) :: (a -> Bool) -> (a -> Bool) -> a -> Bool
 p \/ q = \x -> p x || q x
 
+eq :: Eq a => a -> a -> Bool
+eq = (==)
+
 fromField :: FromField a => ByteString -> Either String a
 fromField =
   AP.parseOnly parseField
@@ -52,13 +55,13 @@ class FromField a where
 -- | See https://www.postgresql.org/docs/current/datatype-binary.html.
 -- Accepts @bytea@.
 instance FromField ByteString where
-  validOid Proxy = Oid.bytea
+  validOid Proxy = eq Oid.bytea
   parseField = AP.takeByteString
 
 -- | See https://www.postgresql.org/docs/current/datatype-character.html.
 -- Accepts @text@, @character@ and @character varying@.
 instance FromField Text where
-  validOid Proxy = Oid.text \/ Oid.character \/ Oid.characterVarying
+  validOid Proxy = eq Oid.text \/ eq Oid.character \/ eq Oid.characterVarying
   parseField = Encoding.decodeUtf8 <$> AP.takeByteString
 
 -- Accepts @text@, @character@ and @character varying@.
@@ -98,22 +101,22 @@ readWord bs = case BS.length bs of
 -- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
 -- We assume that 'Int' has 64 bits. This is not guaranteed but reasonable enough.
 instance FromField Int where
-  validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
+  validOid Proxy = eq Oid.smallint \/ eq Oid.integer \/ eq Oid.bigint
   parseField = readInt =<< AP.takeByteString
 
 -- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
 instance FromField Integer where
-  validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
+  validOid Proxy = eq Oid.smallint \/ eq Oid.integer \/ eq Oid.bigint
   parseField = readInt =<< AP.takeByteString
 
 instance FromField Word where
-  validOid Proxy = Oid.smallint \/ Oid.integer \/ Oid.bigint
+  validOid Proxy = eq Oid.smallint \/ eq Oid.integer \/ eq Oid.bigint
   parseField = readWord =<< AP.takeByteString
 
 -- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
 -- Accepts only @real@ fields, not @double precision@.
 instance FromField Float where
-  validOid Proxy = Oid.real
+  validOid Proxy = eq Oid.real
   -- Afaict there's no cleaner (@base@) way to access the underlying bits.
   -- In C we'd do
   --
@@ -125,7 +128,7 @@ instance FromField Float where
 -- | See https://www.postgresql.org/docs/current/datatype-numeric.html.
 -- Accepts only @double precision@ fields, not @real@.
 instance FromField Double where
-  validOid Proxy = Oid.doublePrecision
+  validOid Proxy = eq Oid.doublePrecision
   parseField = unsafeCoerce <$> readBigEndian @Word <$> AP.takeByteString
 
 boolParser :: Parser Bool
@@ -136,7 +139,7 @@ boolParser = AP.choice
 
 -- | See https://www.postgresql.org/docs/current/datatype-boolean.html.
 instance FromField Bool where
-  validOid Proxy = Oid.boolean
+  validOid Proxy = eq Oid.boolean
   parseField = boolParser
 
 postgresEpoch :: Day
@@ -151,14 +154,14 @@ fromPostgresJulian x = addDays x postgresEpoch
 -- In short, Postgres treats 1 BC as a leap year and doesn't have a year zero.
 -- This means that working with negative dates will be different in Postgres and your application code.
 instance FromField Day where
-  validOid Proxy = Oid.date
+  validOid Proxy = eq Oid.date
   parseField = fromPostgresJulian . fromIntegral <$> readBigEndian @Int32 <$> AP.takeByteString
 
 -- | See https://www.postgresql.org/docs/current/datatype-datetime.html.
 -- Binary format: https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/utils/adt/date.c;h=ae0f24de2c3c54eb6d0405cdb212597c2407238e;hb=HEAD#l1542.
 -- Accepts @time@.
 instance FromField DiffTime where
-  validOid Proxy = Oid.time
+  validOid Proxy = eq Oid.time
   parseField = microsecondsToDiffTime . fromIntegral <$> readBigEndian @Int <$> AP.takeByteString
     where
       microsecondsToDiffTime :: Integer -> DiffTime
@@ -168,7 +171,7 @@ instance FromField DiffTime where
 -- Binary format: https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/backend/utils/adt/date.c;h=ae0f24de2c3c54eb6d0405cdb212597c2407238e;hb=HEAD#l1542.
 -- Accepts @time@.
 instance FromField TimeOfDay where
-  validOid Proxy = Oid.time
+  validOid Proxy = eq Oid.time
   parseField = timeToTimeOfDay <$> parseField @DiffTime
 
 fromPostgresTimestamp :: Int -> (Day, DiffTime)
@@ -181,7 +184,7 @@ fromPostgresTimestamp ts = (day, time)
 -- | See https://www.postgresql.org/docs/current/datatype-datetime.html.
 -- Accepts @timestamp with timezone@.
 instance FromField UTCTime where
-  validOid Proxy = Oid.timestampWithTimezone
+  validOid Proxy = eq Oid.timestampWithTimezone
   parseField = toUTCTime . fromPostgresTimestamp <$> readBigEndian @Int <$> AP.takeByteString
     where
       toUTCTime (day, time) = UTCTime day time
diff --git a/lib/Database/PostgreSQL/Opium/Oid.hs b/lib/Database/PostgreSQL/Opium/Oid.hs
index 83399ec..c5cc748 100644
--- a/lib/Database/PostgreSQL/Opium/Oid.hs
+++ b/lib/Database/PostgreSQL/Opium/Oid.hs
@@ -2,65 +2,62 @@ module Database.PostgreSQL.Opium.Oid where
 
 import Database.PostgreSQL.LibPQ (Oid (..))
 
-eq :: Eq a => a -> a -> Bool
-eq = (==)
-
 -- raw byte string
 
-bytea :: Oid -> Bool
-bytea = eq $ Oid 17
+bytea :: Oid
+bytea = Oid 17
 
 -- string types
 
-text :: Oid -> Bool
-text = eq $ Oid 25
+text :: Oid
+text = Oid 25
 
-character :: Oid -> Bool
-character = eq $ Oid 1042
+character :: Oid
+character = Oid 1042
 
-characterVarying :: Oid -> Bool
-characterVarying = eq $ Oid 1043
+characterVarying :: Oid
+characterVarying = Oid 1043
 
 -- integer types
 
 -- | 16-bit integer
-smallint :: Oid -> Bool
-smallint = eq $ Oid 21
+smallint :: Oid
+smallint = Oid 21
 
 -- | 32-bit integer
-integer :: Oid -> Bool
-integer = eq $ Oid 23
+integer :: Oid
+integer = Oid 23
 
 -- | 64-bit integer
-bigint :: Oid -> Bool
-bigint = eq $ Oid 20
+bigint :: Oid
+bigint = Oid 20
 
 -- floating point types
 
 -- | 32-bit IEEE float
-real :: Oid -> Bool
-real = eq $ Oid 700
+real :: Oid
+real = Oid 700
 
 -- | 64-bit IEEE float
-doublePrecision :: Oid -> Bool
-doublePrecision = eq $ Oid 701
+doublePrecision :: Oid
+doublePrecision = Oid 701
 
--- | Boolean
-boolean :: Oid -> Bool
-boolean = eq $ Oid 16
+-- | Oid
+boolean :: Oid
+boolean = Oid 16
 
 -- | Single days/dates.
-date :: Oid -> Bool
-date = eq $ Oid 1082
+date :: Oid
+date = Oid 1082
 
 -- | Time of day.
-time :: Oid -> Bool
-time = eq $ Oid 1083
+time :: Oid
+time = Oid 1083
 
 -- | A point in time.
-timestamp :: Oid -> Bool
-timestamp = eq $ Oid 1114
+timestamp :: Oid
+timestamp = Oid 1114
 
 -- | A point in time.
-timestampWithTimezone :: Oid -> Bool
-timestampWithTimezone = eq $ Oid 1184
+timestampWithTimezone :: Oid
+timestampWithTimezone = Oid 1184