diff --git a/backends/pardiff/Shpadoinkle/Backend/ParDiff.hs b/backends/pardiff/Shpadoinkle/Backend/ParDiff.hs
index afe73c49e79ec86049748a8e2006d122e79cb1b3..23ddcc526a7dd7e46ca464f0405b88426f3603a6 100644
--- a/backends/pardiff/Shpadoinkle/Backend/ParDiff.hs
+++ b/backends/pardiff/Shpadoinkle/Backend/ParDiff.hs
@@ -15,6 +15,7 @@
 {-# LANGUAGE TypeOperators              #-}
 {-# LANGUAGE UndecidableInstances       #-}
 {-# OPTIONS_GHC -fno-warn-type-defaults #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
 
 #ifndef ghcjs_HOST_OS
 {-# LANGUAGE StandaloneDeriving         #-}
@@ -45,7 +46,7 @@ module Shpadoinkle.Backend.ParDiff
 
 
 import           Control.Applicative         (Alternative)
-import           Control.Compactable         (Compactable (traverseMaybe))
+import           Control.Compactable         (Compactable (..))
 import           Control.Lens                ((^.))
 import           Control.Monad.Base          (MonadBase (..), liftBaseDefault)
 import           Control.Monad.Catch         (MonadCatch, MonadThrow)
@@ -56,11 +57,13 @@ import           Control.Monad.Trans.Control (ComposeSt, MonadBaseControl (..),
                                               MonadTransControl,
                                               defaultLiftBaseWith,
                                               defaultRestoreM)
-import           Data.Align                  (Semialign (align))
+import           Data.Align                  (Semialign (..))
+import           Data.FMList                 as FM
 import           Data.Foldable               (traverse_)
 import           Data.Kind                   (Type)
 import           Data.Map                    (Map)
 import qualified Data.Map                    as M
+import           Data.Maybe                  (fromJust, isJust)
 import           Data.Monoid                 ((<>))
 import           Data.Once                   (Once, newOnce, runOnce)
 import           Data.Text                   (Text, intercalate)
@@ -138,8 +141,20 @@ runParDiff :: TVar model -> ParDiffT model m ~> m
 runParDiff t (ParDiffT r) = runReaderT r t
 
 
+instance Compactable FMList where
+  compact = fmap fromJust . FM.filter isJust
+
+instance Semialign FMList where
+  align xs ys | FM.null ys = This <$> xs
+  align xs ys | FM.null xs = That <$> ys
+  align xs ys = let x = FM.head xs
+                    y = FM.head ys
+                 in FM.cons (These x y) (align (FM.tail xs) (FM.tail ys))
+  zip = FM.zip
+
+
 data ParVNode :: Type -> Type where
-  ParNode     :: Once JSM RawNode -> Text -> Map Text (ParVProp a) -> [ParVNode a] -> ParVNode a
+  ParNode     :: Once JSM RawNode -> Text -> Map Text (ParVProp a) -> FMList (ParVNode a) -> ParVNode a
   ParPotato   :: Once JSM RawNode -> ParVNode a
   ParTextNode :: Once JSM RawNode -> Text -> ParVNode a
 
@@ -326,7 +341,7 @@ patchChildren
 #endif
   => Show a
   => NFData a
-  => RawNode -> [ParVNode a] -> [ParVNode a] -> ParDiffT a m [ParVNode a]
+  => RawNode -> FMList (ParVNode a) -> FMList (ParVNode a) -> ParDiffT a m (FMList (ParVNode a))
 patchChildren parent@(RawNode p) old new'' =
   traverseMaybe (\case
 
diff --git a/backends/pardiff/package.yaml b/backends/pardiff/package.yaml
index 218a3172a0adec90cbf58dd94d237a461ed476fa..94751bf8791194556f1e5d065e3b0a931903a141 100644
--- a/backends/pardiff/package.yaml
+++ b/backends/pardiff/package.yaml
@@ -53,6 +53,7 @@ library:
     - semialign            >= 1 && < 1.2
     - these                >= 1 && < 1.2
     - transformers-base    >= 0.4.5 && < 0.5
+    - fmlist
 
     - Shpadoinkle
 
diff --git a/backends/snabbdom/Shpadoinkle/Backend/Snabbdom.hs b/backends/snabbdom/Shpadoinkle/Backend/Snabbdom.hs
index be5ef61f517b4daf8b033e71bf5a3a9d05d71f4b..e36d8ef772d1e9d2edf43ce825eea548ea69c829 100644
--- a/backends/snabbdom/Shpadoinkle/Backend/Snabbdom.hs
+++ b/backends/snabbdom/Shpadoinkle/Backend/Snabbdom.hs
@@ -40,6 +40,7 @@ import           Control.Monad.Trans.Control (ComposeSt, MonadBaseControl (..),
                                               MonadTransControl,
                                               defaultLiftBaseWith,
                                               defaultRestoreM)
+import           Data.FMList                 as FM
 import           Data.FileEmbed              (embedStringFile)
 import           Data.Text                   (Text, split)
 import           Data.Traversable            (for)
@@ -184,7 +185,7 @@ instance (MonadJSM m, NFData a) => Backend (SnabbdomT a) m a where
       cs <- sequence children
       i <- ask; liftJSM $ do
         o <- props toJSM i $ fromProps ps
-        jsg3 "vnode" name o cs >>= fromJSValUnchecked)
+        jsg3 "vnode" name o (FM.toList cs) >>= fromJSValUnchecked)
 
     (\mrn -> liftJSM $ do
       o <- create
diff --git a/backends/snabbdom/package.yaml b/backends/snabbdom/package.yaml
index 22680ef280a3c971e35d47797e1ae3a82692861a..0e9c269e034a0b26a9968616efab0da95f27c07d 100644
--- a/backends/snabbdom/package.yaml
+++ b/backends/snabbdom/package.yaml
@@ -44,6 +44,7 @@ library:
     - exceptions
     - transformers-base
     - monad-control
+    - fmlist
 
     - mtl        >= 2.2.2 && < 2.3
     - unliftio   >= 0.2.12 && < 0.3
diff --git a/backends/static/Shpadoinkle/Backend/Static.hs b/backends/static/Shpadoinkle/Backend/Static.hs
index 04083b659d92950751f936306045d5b8946c5449..bebee22a5c8cce260f19bd221348ec6fe31b8058 100644
--- a/backends/static/Shpadoinkle/Backend/Static.hs
+++ b/backends/static/Shpadoinkle/Backend/Static.hs
@@ -11,7 +11,9 @@ module Shpadoinkle.Backend.Static ( renderStatic ) where
 
 
 import           Control.Compactable (Compactable (fmapMaybe))
-import           Data.Monoid         (mconcat, (<>))
+import           Data.FMList         as FM
+import           Data.Foldable       (fold)
+import           Data.Monoid         ((<>))
 import           Data.Text           (Text, null, unwords)
 
 import           Shpadoinkle         (Html, Prop (PText), cataH, cataProp)
@@ -22,7 +24,7 @@ renderStatic :: Html m a -> Text
 renderStatic = cataH renderTag (const mempty) id
 
 
-renderTag :: Text -> [(Text, Prop m a)] -> [Text] -> Text
+renderTag :: Text -> [(Text, Prop m a)] -> FMList Text -> Text
 renderTag tag props cs
   | isSelfClosing tag = renderSelfClosing tag props
   | otherwise         = renderWrapping tag props cs
@@ -38,12 +40,12 @@ innerHTML :: Text
 innerHTML = "innerHTML"
 
 
-renderWrapping :: Text -> [(Text, Prop m a)] -> [Text] -> Text
+renderWrapping :: Text -> [(Text, Prop m a)] -> FMList Text -> Text
 renderWrapping tag props cs =
   renderOpening tag props <> ">"
   <> (case innerHTML `lookup` props of
         Just (PText html) -> html
-        _                 -> mconcat cs)
+        _                 -> fold cs)
   <> "</" <> tag <> ">"
 
 
diff --git a/backends/static/package.yaml b/backends/static/package.yaml
index 2efafe13d4ee9af53b4d80430b1a9b59001f8bd1..023fe4f6353120dbe64fddcac32a01a1d216527f 100644
--- a/backends/static/package.yaml
+++ b/backends/static/package.yaml
@@ -38,5 +38,6 @@ library:
   dependencies:
     - compactable >= 0.1.2 && < 0.2
     - text        >= 1.2.3 && < 1.3
+    - fmlist
 
     - Shpadoinkle
diff --git a/core/Shpadoinkle/Core.hs b/core/Shpadoinkle/Core.hs
index f77f6e7b83e92d798caf75fb1977af79165630c7..e79bf0992e051852afca93f7325861352f1815bf 100644
--- a/core/Shpadoinkle/Core.hs
+++ b/core/Shpadoinkle/Core.hs
@@ -59,6 +59,7 @@ import           Control.PseudoInverseCategory (EndoIso (..),
                                                 PIArrow (piendo, piiso),
                                                 PseudoInverseCategory (piinverse),
                                                 ToHask (piapply))
+import           Data.FMList                   as FM
 import           Data.Kind                     (Type)
 import           Data.Map                      as M (Map, singleton, toList,
                                                      unionWithKey)
@@ -87,7 +88,7 @@ import           Shpadoinkle.Continuation      (Continuation, Continuous (..),
 -- This is Church encoded for performance reasons.
 newtype Html m a = Html
   { unHtml
-      :: forall r. (Text -> Props m a -> [r] -> r)
+      :: forall r. (Text -> Props m a -> FMList r-> r)
       -> (JSM RawNode -> r)
       -> (Text -> r)
       -> r
@@ -134,7 +135,7 @@ newtype Props m a = Props { getProps :: Map Text (Prop m a) }
 
 
 toProps :: Applicative m => [(Text, Prop m a)] -> Props m a
-toProps = foldMap $ Props . uncurry singleton
+toProps = foldMap $ Props . uncurry M.singleton
 
 
 fromProps :: Props m a -> [(Text, Prop m a)]
@@ -311,7 +312,7 @@ cataProp d t f l p = \case
 
 -- | Construct an HTML element JSX-style.
 h :: Applicative m => Text -> [(Text, Prop m a)] -> [Html m a] -> Html m a
-h t ps cs = Html $ \a b c -> a t (toProps ps) ((\(Html h') -> h' a b c) <$> cs)
+h t ps cs = Html $ \a b c -> a t (toProps ps) ((\(Html h') -> h' a b c) <$> FM.fromList cs)
 {-# INLINE h #-}
 
 
@@ -334,7 +335,7 @@ eitherH = eitherC
 
 
 -- | Fold an HTML element, i.e. transform an h-algebra into an h-catamorphism.
-cataH :: (Text -> [(Text, Prop m a)] -> [b] -> b)
+cataH :: (Text -> [(Text, Prop m a)] -> FMList b -> b)
       -> (JSM RawNode -> b)
       -> (Text -> b)
       -> Html m a -> b
diff --git a/core/package.yaml b/core/package.yaml
index 853515d5db3f1d759ae54899cbe8dab466953ebb..bd6488cb00edffa740502656a15dcdca7b5ac499 100644
--- a/core/package.yaml
+++ b/core/package.yaml
@@ -31,6 +31,7 @@ dependencies:
     - base >= 4.12.0 && < 4.16
     - transformers
     - containers
+    - fmlist
 
 
 when: