diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,11 @@
+2021-07-07
+        * Version bump (3.4). (#231)
+        * Deprecated `Copilot.Core.Locals`. (#141)
+        * Deprecated `Copilot.Core.Type.Read` module. (#144)
+        * Deprecated `showWit`. (#140)
+        * Deprecated `Copilot.Core.Type.Eq`. (#143)
+        * Remove unused module `Copilot.Core.StructMarshal`. (#139)
+
 2021-05-07
         * Version bump (3.3). (#217)
         * Fix URL in bug-reports field in cabal file. (#215)
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:             3.3
+version:             3.4
 synopsis:            An intermediate representation for Copilot.
 description:
   Intermediate representation for Copilot.
diff --git a/src/Copilot/Core/Locals.hs b/src/Copilot/Core/Locals.hs
--- a/src/Copilot/Core/Locals.hs
+++ b/src/Copilot/Core/Locals.hs
@@ -13,6 +13,7 @@
 {-# LANGUAGE ExistentialQuantification #-}
 
 module Copilot.Core.Locals
+  {-# DEPRECATED "This module is deprecated." #-}
   ( Loc (..)
   , locals
   ) where
diff --git a/src/Copilot/Core/Type/Eq.hs b/src/Copilot/Core/Type/Eq.hs
--- a/src/Copilot/Core/Type/Eq.hs
+++ b/src/Copilot/Core/Type/Eq.hs
@@ -6,6 +6,7 @@
 {-# LANGUAGE ExistentialQuantification, GADTs #-}
 
 module Copilot.Core.Type.Eq
+  {-# DEPRECATED "This module is deprecated." #-}
   ( EqWit (..)
   , eqWit
   , UVal (..)
@@ -47,18 +48,18 @@
 
 instance Eq UVal where
   (==) UVal { uType = t1
-            , uVal = a } 
+            , uVal = a }
        UVal { uType = t2
             , uVal = b }
     = case eqWit t1 of
-        EqWit -> 
+        EqWit ->
           case eqWit t2 of
-            EqWit -> 
+            EqWit ->
               let dyn1 = toDyn t1 a in
               case fromDyn t2 dyn1 of
                 Nothing -> False
-                Just x  -> 
-                  case t1 of 
+                Just x  ->
+                  case t1 of
                     -- Hacks for QuickChecking between C and Haskell
                     Float  -> case t2 of
                                 Float -> approx floatErr x b
@@ -66,10 +67,10 @@
                                                     "copilot-core"
                     Double -> case t2 of
                                 Double -> approx doubleErr x b
-                                _      -> impossible "instance Eq UVal" 
+                                _      -> impossible "instance Eq UVal"
                                                      "copilot-core"
                     _      -> x == b
-    where 
+    where
     approx :: (Num a, Ord a) => a -> a -> a -> Bool
     approx err x y = x - y < err && y - x < err
     floatErr  = 0.0001 :: Float
diff --git a/src/Copilot/Core/Type/Read.hs b/src/Copilot/Core/Type/Read.hs
--- a/src/Copilot/Core/Type/Read.hs
+++ b/src/Copilot/Core/Type/Read.hs
@@ -6,6 +6,7 @@
 {-# LANGUAGE ExistentialQuantification, GADTs #-}
 
 module Copilot.Core.Type.Read
+  {-# DEPRECATED "This module is deprecated." #-}
   ( ReadWit (..)
   , readWit
   , readWithType
diff --git a/src/Copilot/Core/Type/Show.hs b/src/Copilot/Core/Type/Show.hs
--- a/src/Copilot/Core/Type/Show.hs
+++ b/src/Copilot/Core/Type/Show.hs
@@ -24,6 +24,7 @@
 --------------------------------------------------------------------------------
 
 -- | Turn a type into a show witness.
+{-# DEPRECATED showWit "This function is deprecated in Copilot 3.4." #-}
 showWit :: Type a -> ShowWit a
 showWit t =
   case t of