diff --git a/src/Nixfmt/Predoc.hs b/src/Nixfmt/Predoc.hs
index 9741a5c3..d265bb37 100644
--- a/src/Nixfmt/Predoc.hs
+++ b/src/Nixfmt/Predoc.hs
@@ -166,9 +166,11 @@ trailing t = [Text 0 0 Trailing t]
 group :: (HasCallStack) => (Pretty a) => a -> Doc
 group x =
   pure . Group RegularG $
-    if p /= [] && (isSoftSpacing (head p) || isSoftSpacing (last p))
-      then error $ "group should not start or end with whitespace, use `group'` if you are sure; " <> show p
-      else p
+    case p of
+      (headP : _)
+        | isSoftSpacing headP || isSoftSpacing (last p) ->
+            error $ "group should not start or end with whitespace, use `group'` if you are sure; " <> show p
+      _ -> p
   where
     p = pretty x
 
@@ -631,9 +633,9 @@ layoutGreedy tw iw doc = Text.concat $ evalState (go [Group RegularG doc] []) (0
         then
           let -- We know that the last printed character was a line break (cc == 0),
               -- therefore drop any leading whitespace within the group to avoid duplicate newlines
-              grp' = case head grp of
-                Spacing _ -> tail grp
-                Group ann ((Spacing _) : inner) -> Group ann inner : tail grp
+              grp' = case grp of
+                Spacing _ : tl -> tl
+                Group ann ((Spacing _) : inner) : tl -> Group ann inner : tl
                 _ -> grp
               (nl, off) = nextIndent grp'
 
diff --git a/src/Nixfmt/Types.hs b/src/Nixfmt/Types.hs
index 1ddac3d0..d964eadd 100644
--- a/src/Nixfmt/Types.hs
+++ b/src/Nixfmt/Types.hs
@@ -372,7 +372,7 @@ instance LanguageElement Term where
 
   walkSubprograms = \case
     -- Map each item to a singleton list, then handle that
-    (List _ items _) | Prelude.length (unItems items) == 1 -> case Prelude.head (unItems items) of
+    (List _ (Items [singleItem]) _) -> case singleItem of
       (Item item) -> [Term item]
       (Comments _) -> []
     (List open items close) ->
@@ -381,7 +381,7 @@ instance LanguageElement Term where
           [Term (List (stripTrivia open) (Items [Item item]) (stripTrivia close))]
         Comments c ->
           [Term (List (stripTrivia open) (Items [Comments c]) (stripTrivia close))]
-    (Set _ _ items _) | Prelude.length (unItems items) == 1 -> case Prelude.head (unItems items) of
+    (Set _ _ (Items [singleItem]) _) -> case singleItem of
       (Item (Inherit _ from sels _)) ->
         (Term <$> maybeToList from) ++ concatMap walkSubprograms sels
       (Item (Assignment sels _ expr _)) ->