diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 ## Changelog
 
+## 0.21.1.0 (2018-03-09)
+
+* fay 0.24.0.0 support
+
 ## 0.21.0.0 (2017-08-02)
 
 * Changed the definition of `splitOn` from `Char -> Text -> [Text]` to `Text -> Text -> [Text]` to make it more general and to match `text:Data.Text.splitOn`. Thanks to A. Bram Neijt!
diff --git a/fay-base.cabal b/fay-base.cabal
--- a/fay-base.cabal
+++ b/fay-base.cabal
@@ -1,5 +1,5 @@
 name:                fay-base
-version:             0.21.0.0
+version:             0.21.1.0
 synopsis:            The base package for Fay.
 description:         The base package for Fay.
                      This package amongst others exports Prelude and FFI which you probably want to use with Fay.
@@ -59,4 +59,4 @@
     Unsafe.Coerce
   build-depends:
       base == 4.*
-    , fay >= 0.21.1 && < 0.24
+    , fay >= 0.21.1 && < 0.25
diff --git a/src/Data/MutMap.hs b/src/Data/MutMap.hs
--- a/src/Data/MutMap.hs
+++ b/src/Data/MutMap.hs
@@ -22,7 +22,6 @@
 import Data.Defined
 import Data.MutMap.Internal
 import Data.Text (Text)
-import qualified Data.Text as T
 import FFI
 import Prelude
 
@@ -37,7 +36,7 @@
 mutFromList = mutFromListI . map (\(key, val) -> KeyValI (addSalt key) val)
 
 mutFromListI :: [KeyValI a] -> Fay (MutMap a)
-mutFromListI = ffi "function() { var r = {}; $.each(%1, function(ix, x) { r[x.slot1] = x.slot2; }); return r; }()"
+mutFromListI = ffi "function() { var r = {}; for(var key in %1) { r[%1[key].slot1] = %1[key].slot2; } return r; }()"
 
 -- Query
 
@@ -63,21 +62,21 @@
 mutAssocsI = ffi "function() { var r = []; for (var k in %1) { r.push({ instance : 'KeyValI', slot1 : k, slot2 : %1[k] }); } return r; }()"
 
 mutClone :: MutMap a -> Fay (MutMap a)
-mutClone = ffi "jQuery['extend']({}, %1)"
+mutClone = ffi "Fay$$objConcat({}, %1)"
 
 -- Note: Also clones.
 mutMapM :: (a -> Fay b) -> MutMap a -> MutMap b
-mutMapM = ffi "jQuery['map'](jQuery['extend']({}, %2), %1)"
+mutMapM = ffi "function () { var r = {}; for(var key in %2){ r[key] = %1(%2[key]); } return r;}()"
 
 mutMapM_ :: (a -> Fay ()) -> MutMap a -> Fay ()
-mutMapM_ = ffi "jQuery['map'](%2, function(x) { %1(x); return x; })"
+mutMapM_ = ffi "function () { var r = {}; for(var key in %2){ %1(%2[key]); } return;}()"
 
 -- Note: Also clones.
 mutMapMaybeM :: (a -> Fay (Maybe b)) -> MutMap a -> MutMap b
 mutMapMaybeM f = mutMapMaybeMI $ \x -> f x >>= return . toDefined
 
 mutMapMaybeMI :: (a -> Fay (Defined b)) -> MutMap a -> MutMap b
-mutMapMaybeMI = ffi "jQuery['map']($['extend']({}, %2), %1)"
+mutMapMaybeMI = ffi "function () { var r = {}; for(var key in %2){ r[key] = %1(%2[key]); } return r;}()"
 
 -- Mutation
 
diff --git a/src/Data/Ratio.hs b/src/Data/Ratio.hs
--- a/src/Data/Ratio.hs
+++ b/src/Data/Ratio.hs
@@ -27,9 +27,10 @@
 (%) :: Int -> Int -> Rational
 x % y = reduce (x * signum y) (abs y)
   where reduce :: Int -> Int -> Rational
-        reduce x y | y == 0    = error "can't devide by zero"
-                   | otherwise = let d = gcd x y
-                                 in Ratio (x `quot` d) (y `quot` d)
+        reduce x' y' = if y' == 0
+                       then error "can't devide by zero"
+                       else let d = gcd x' y'
+                            in Ratio (x' `quot` d) (y' `quot` d)
 
 numerator, denominator :: Rational -> Int
 numerator (Ratio n _) = n
diff --git a/src/Data/Time.hs b/src/Data/Time.hs
--- a/src/Data/Time.hs
+++ b/src/Data/Time.hs
@@ -65,4 +65,4 @@
 -- | Show a day. Meant for debugging purposes, not production presentation.
 showDay :: Day -> Text
 showDay =
-  ffi "date.getUTCFullYear() + ' ' + showMonth(date) + ' ' + (date.getUTCDate() + 1)"
+  ffi "(%1).getUTCFullYear() + ' ' + ((%1).getUTCMonth() + 1) + ' ' + ((%1).getUTCDate() + 1)"
diff --git a/src/Data/Var.hs b/src/Data/Var.hs
--- a/src/Data/Var.hs
+++ b/src/Data/Var.hs
@@ -144,7 +144,7 @@
 subscribeAndRead :: Var a -> (a -> Fay void) -> Fay (() -> Fay ())
 subscribeAndRead v f = do
   x <- get v
-  f x
+  _ <- f x
   subscribe v f
 
 -- | Subscribe to a 'Var', but only call handler when it actually changes, and
diff --git a/src/Prelude.hs b/src/Prelude.hs
--- a/src/Prelude.hs
+++ b/src/Prelude.hs
@@ -209,7 +209,9 @@
   )
   where
 
+#ifdef FAY
 import           Data.Data
+#endif
 import           Fay.FFI
 import           "base" Prelude   (Bool (True, False), Eq, seq, (&&), (/=),
                                    (==), (||))
@@ -290,7 +292,7 @@
 
 -- | Monomorphic return for Fay.
 return :: a -> Fay a
-return = ffi "Fay$$return(%1)"
+return = ffi "Fay$$$_return(%1)"
 
 fail :: String -> Fay a
 fail = error
@@ -792,7 +794,7 @@
 
 init :: [a] -> [a]
 init []    = error "init: empty list"
-init [a]   = []
+init [_]   = []
 init (h:t) = h : init t
 
 last :: [a] -> a
@@ -824,7 +826,7 @@
 drop :: Int -> [a] -> [a]
 drop 0 xs = xs
 drop _ [] = []
-drop n xss@(x:xs) = if n < 0 then xss
+drop n xss@(_:xs) = if n < 0 then xss
                              else drop (n-1) xs
 
 splitAt :: Int -> [a] -> ([a], [a])