diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,9 @@
+2024-11-07
+        * Version bump (4.1). (#561)
+        * Add Haddocks for updateField. (#525)
+        * Standardize changelog format. (#550)
+        * Deprecate Copilot.Core.Type.UType.uTypeType. (#484)
+
 2024-09-07
         * Version bump (4.0). (#532)
         * Update Op3, Array to support array updates. (#36)
@@ -136,15 +142,15 @@
         * Version bump (3.2.1). (#136)
         * Completed the documentation. (#145)
 
-2020-12-06 Ivan Perez <ivan.perez@acm.org>
-        * Version bump (3.2).
-        * Fixed implementation of tysize for n-dimensional arrays. (#147).
-        * Removed sorting of interpreter output (#148).
-        * Minor documentation fixes (#149, #151).
+2020-12-06
+        * Version bump (3.2). (#65)
+        * Fixed implementation of tysize for n-dimensional arrays. (#147)
+        * Removed sorting of interpreter output. (#148)
+        * Minor documentation fixes. (#149, #151)
         * Credits: @fdedden.
 
-2019-11-22 Ivan Perez <ivan.perez@nianet.org>
-        * Version bump (3.1).
-        * Eliminate random modules and generators (#157).
-        * Updated contact information for 'impossible' error (#154).
-        * Implement missing pretty printer for Index operator (#155).
+2019-11-22
+        * Version bump (3.1). (#46)
+        * Eliminate random modules and generators. (#157)
+        * Updated contact information for 'impossible' error. (#154)
+        * Implement missing pretty printer for Index operator. (#155)
diff --git a/copilot-core.cabal b/copilot-core.cabal
--- a/copilot-core.cabal
+++ b/copilot-core.cabal
@@ -1,6 +1,6 @@
 cabal-version:       >=1.10
 name:                copilot-core
-version:             4.0
+version:             4.1
 synopsis:            An intermediate representation for Copilot.
 description:
   Intermediate representation for Copilot.
diff --git a/src/Copilot/Core/Type.hs b/src/Copilot/Core/Type.hs
--- a/src/Copilot/Core/Type.hs
+++ b/src/Copilot/Core/Type.hs
@@ -60,8 +60,30 @@
   -- | Transforms all the struct's fields into a list of values.
   toValues :: a -> [Value a]
 
+  -- | Update the value of a struct field. This is only used by the Copilot
+  -- interpreter, so if you do not plan to use the interpreter, it is safe to
+  -- omit an implementation of this method.
+  --
+  -- In order to implement 'updateField', you should do the following for each
+  -- 'Field' in a struct:
+  --
+  -- 1. Check that the name of the 'Field' matches the name of the supplied
+  --    'Value' (using 'GHC.TypeLits.sameSymbol').
+  --
+  -- 2. Check that the type of the 'Field' matches the 'Type' of the supplied
+  --    'Value' (using 'DE.testEquality').
+  --
+  -- 3. If both (1) and (2) succeed, update the corresponding struct field using
+  --    a record update.
+  --
+  -- For a complete end-to-end example that demonstrates how to implement
+  -- 'updateField' and use it in the Copilot interpreter, see the
+  -- @examples/StructsUpdateField.hs@ example in the @copilot@ library.
   updateField :: a -> Value t -> a
-  updateField = error "Field updates not supported for this type."
+  updateField = error $ unlines
+    [ "Field updates not supported for this type."
+    , "(Perhaps you need to implement 'updateField' for a 'Struct' instance?)"
+    ]
 
 -- | The field of a struct, together with a representation of its type.
 data Value a =
@@ -246,6 +268,7 @@
 
 -- | A untyped type (no phantom type).
 data UType = forall a . Typeable a => UType { uTypeType :: Type a }
+{-# DEPRECATED uTypeType "This field is deprecated in Copilot 4.1. Use pattern matching instead." #-}
 
 instance Eq UType where
   UType ty1 == UType ty2 = typeRep ty1 == typeRep ty2