diff --git a/ChangeLog.md b/ChangeLog.md
index 396a520..116e0ab 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -4,6 +4,10 @@
 
 See https://github.com/chungyc/ninetynine.
 
+## v1.3.0
+
+*   Update to Haskell Stack LTS 22.23.
+
 ## v1.2.0
 
 *   No longer require the implementation of partial functions.
diff --git a/ninetynine.cabal b/ninetynine.cabal
index 6445999..0da43a9 100644
--- a/ninetynine.cabal
+++ b/ninetynine.cabal
@@ -5,7 +5,7 @@ cabal-version: 2.2
 -- see: https://github.com/sol/hpack
 
 name:           ninetynine
-version:        1.2.0
+version:        1.3.0
 synopsis:       Ninety-Nine Haskell Problems
 description:    Ninety-Nine Haskell Problems.
                 These are programming exercises for practice with [Haskell](https://www.haskell.org/).
diff --git a/package.yaml b/package.yaml
index aeff6d6..d9224a6 100644
--- a/package.yaml
+++ b/package.yaml
@@ -1,11 +1,11 @@
 name:                ninetynine
-version:             1.2.0
+version:             1.3.0
 github:              "chungyc/ninetynine"
 license:             GPL-3.0-or-later
 license-file:        LICENSE
 author:              "Yoo Chung"
 maintainer:          "dev@chungyc.org"
-copyright:           "Copyright (C) 2023 Yoo Chung"
+copyright:           "Copyright (C) 2024 Yoo Chung"
 homepage:            "https://ninetynine.haskell.chungyc.org/"
 
 extra-source-files:
diff --git a/src/Solutions/P78.hs b/src/Solutions/P78.hs
index 6199d67..6919a66 100644
--- a/src/Solutions/P78.hs
+++ b/src/Solutions/P78.hs
@@ -9,6 +9,7 @@ Some solutions to "Problems.P78" of Ninety-Nine Haskell "Problems".
 module Solutions.P78 (collatz) where
 
 import           Control.Monad.Writer
+import           Data.Monoid (Sum(..))
 
 {- | Starting from a positive integer \(n\),
 we can have a sequence of numbers such that at each step,
diff --git a/src/Solutions/P79.hs b/src/Solutions/P79.hs
index 031c616..2623624 100644
--- a/src/Solutions/P79.hs
+++ b/src/Solutions/P79.hs
@@ -8,6 +8,7 @@ Some solutions to "Problems.P79" of Ninety-Nine Haskell "Problems".
 -}
 module Solutions.P79 (calculatePostfix) where
 
+import           Control.Monad (guard, mzero)
 import           Control.Monad.Identity
 import           Control.Monad.State
 import           Control.Monad.Trans.Maybe
diff --git a/stack.yaml b/stack.yaml
index 639f176..f627bc1 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -5,7 +5,7 @@
 # Resolver to choose a 'specific' stackage snapshot or a compiler version.
 # A snapshot resolver dictates the compiler version and the set of packages
 # to be used for project dependencies.
-resolver: lts-21.24
+resolver: lts-22.23
 
 # User packages to be built.
 packages: