diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,4 +1,8 @@
 2024-01-07
+        * Version bump (3.18.1). (#493)
+        * Adjust to work with GHC 9.6. (#491)
+
+2024-01-07
         * Version bump (3.18). (#487)
         * Introduce testing infrastructure for Copilot.Theorem.What4. (#474)
         * Replace uses of forall with forAll. (#470)
diff --git a/copilot-theorem.cabal b/copilot-theorem.cabal
--- a/copilot-theorem.cabal
+++ b/copilot-theorem.cabal
@@ -14,7 +14,7 @@
   <https://copilot-language.github.io>.
 
 
-version                   : 3.18
+version                   : 3.18.1
 license                   : BSD3
 license-file              : LICENSE
 maintainer                : Ivan Perez <ivan.perezdominguez@nasa.gov>
@@ -63,8 +63,8 @@
                           , xml                   >= 1.3 && < 1.4
                           , what4                 >= 1.3 && < 1.6
 
-                          , copilot-core          >= 3.18 && < 3.19
-                          , copilot-prettyprinter >= 3.18 && < 3.19
+                          , copilot-core          >= 3.18.1 && < 3.19
+                          , copilot-prettyprinter >= 3.18.1 && < 3.19
 
   exposed-modules         : Copilot.Theorem
                           , Copilot.Theorem.Prove
diff --git a/src/Copilot/Theorem/IL/Translate.hs b/src/Copilot/Theorem/IL/Translate.hs
--- a/src/Copilot/Theorem/IL/Translate.hs
+++ b/src/Copilot/Theorem/IL/Translate.hs
@@ -14,6 +14,7 @@
 
 import qualified Data.Map.Strict as Map
 
+import Control.Monad       (forM, liftM2, when)
 import Control.Monad.State
 
 import Data.Char
diff --git a/src/Copilot/Theorem/Misc/Utils.hs b/src/Copilot/Theorem/Misc/Utils.hs
--- a/src/Copilot/Theorem/Misc/Utils.hs
+++ b/src/Copilot/Theorem/Misc/Utils.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE Safe #-}
+{-# LANGUAGE Trustworthy #-}
 
 -- | Utility / auxiliary functions.
 module Copilot.Theorem.Misc.Utils
diff --git a/src/Copilot/Theorem/Prove.hs b/src/Copilot/Theorem/Prove.hs
--- a/src/Copilot/Theorem/Prove.hs
+++ b/src/Copilot/Theorem/Prove.hs
@@ -22,6 +22,7 @@
 
 import Data.List (intercalate)
 import Control.Applicative (liftA2)
+import Control.Monad        (ap, liftM)
 import Control.Monad.Writer
 
 -- | Output produced by a prover, containing the 'Status' of the proof and
diff --git a/src/Copilot/Theorem/TransSys/Translate.hs b/src/Copilot/Theorem/TransSys/Translate.hs
--- a/src/Copilot/Theorem/TransSys/Translate.hs
+++ b/src/Copilot/Theorem/TransSys/Translate.hs
@@ -47,6 +47,7 @@
 import Copilot.Theorem.TransSys.Cast
 import Copilot.Theorem.Misc.Utils
 
+import Control.Monad            (liftM, liftM2, unless)
 import Control.Monad.State.Lazy
 
 import Data.Char (isNumber)
diff --git a/src/Copilot/Theorem/What4.hs b/src/Copilot/Theorem/What4.hs
--- a/src/Copilot/Theorem/What4.hs
+++ b/src/Copilot/Theorem/What4.hs
@@ -57,6 +57,7 @@
 import qualified What4.Solver                   as WS
 import qualified What4.Solver.DReal             as WS
 
+import Control.Monad (forM)
 import Control.Monad.State
 import qualified Data.BitVector.Sized as BV
 import Data.Foldable (foldrM)