diff --git a/.circleci/config.yml b/.circleci/config.yml
index 6ff228bc..a1da7d6a 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -3,7 +3,7 @@ jobs:
   build:
     # Ref: https://mmhaskell.com/blog/2018/4/25/dockerizing-our-haskell-app
     docker:
-    - image: haskell:8.6.3
+    - image: haskell:8.8.4
     steps:
     - run: apt update
     - run: apt install -y zip jq curl
@@ -18,8 +18,9 @@ jobs:
         - 'dependencies-'
     # 下記のパッケージはビルド時にメモリが不足するため、一旦 -j1 でビルドしておく
     # Ref: https://haskell.e-bigmoon.com/posts/2017/12-31-travis-out-of-memory.html
-    - run: stack build --compiler=ghc-8.6.3 --no-terminal -j1 Cabal wai-logger
-    - run: stack build --compiler=ghc-8.6.3 --no-terminal --only-dependencies
+    - run: stack build --compiler=ghc-8.8.4 --no-terminal -j1 Cabal wai-logger
+    - run: stack build --compiler=ghc-8.8.4 --no-terminal -j1 pandoc
+    - run: stack build --compiler=ghc-8.8.4 --no-terminal --only-dependencies
     - save_cache:
         key: 'dependencies-{{ checksum "stack.yaml" }}-{{ checksum "haskell-jp-blog.cabal" }}'
         paths:
@@ -30,7 +31,7 @@ jobs:
         keys:
         - 'executable-{{ checksum "src/site.hs" }}'
         - 'executable-'
-    - run: stack --compiler=ghc-8.6.3 --local-bin-path='.' --no-terminal install --pedantic
+    - run: stack --compiler=ghc-8.8.4 --local-bin-path='.' --no-terminal install --pedantic
     - save_cache:
         key: 'executable-{{ checksum "src/site.hs" }}'
         paths:
@@ -58,7 +59,7 @@ jobs:
 
   deploy:
     docker:
-    - image: haskell:8.6.3
+    - image: haskell:8.8.4
     steps:
     - checkout:
         path: ~/project
diff --git a/haskell-jp-blog.cabal b/haskell-jp-blog.cabal
index c6ceb682..e681d91c 100644
--- a/haskell-jp-blog.cabal
+++ b/haskell-jp-blog.cabal
@@ -15,6 +15,7 @@ executable site
                   , pandoc-types
                   , skylighting
                   , filepath
+                  , text
   ghc-options:      -threaded -Wall
   default-language: Haskell2010
 
diff --git a/src/site.hs b/src/site.hs
index 8896cf26..97a029f7 100644
--- a/src/site.hs
+++ b/src/site.hs
@@ -12,7 +12,8 @@ import Data.Data (Data)
 import Data.Default (def)
 import Data.List.NonEmpty (NonEmpty((:|)), groupBy, toList)
 import Data.Maybe (fromMaybe)
-import Data.Monoid ((<>))
+import Data.Text (Text)
+import qualified Data.Text as Text
 import qualified Data.Tree as Tree
 import Data.Typeable (Typeable)
 import Hakyll
@@ -184,12 +185,12 @@ createSubHeadingContentForPost item = do
         tagsHtml = maybe "" (\tags -> "<span class=\"meta\">Tags: " ++ tags ++ "</span>") mtags
     return $ subHeadingHtml ++ postedByHtml ++ tagsHtml
 
-isDraftPost :: MonadMetadata m => Identifier -> m Bool
+isDraftPost :: (MonadMetadata m, MonadFail m) => Identifier -> m Bool
 isDraftPost ident = do
     isDraft <- fromMaybe "false" <$> getMetadataField ident "draft"
     return $ isDraft == "true"
 
-postItemIdentifiers :: MonadMetadata m => m [Identifier]
+postItemIdentifiers :: (MonadMetadata m, MonadFail m) => m [Identifier]
 postItemIdentifiers = do
     idents <- getMatches "posts/**"
     idents' <- filterM (fmap not . isDraftPost) idents
@@ -254,7 +255,7 @@ addSpaceAroundAsciiInlines = concatMap addSpaceInline
 -- 'textLangToInline'.  Blocks of Latin text will be placed in @\<span\>@ tags
 -- with an @\"ascii\"@ class.
 addSpaceInline :: Inline -> [Inline]
-addSpaceInline (Str string) = textLangToInline <$> splitOnLanguage string
+addSpaceInline (Str text) = textLangToInline <$> splitOnLanguage (Text.unpack text)
 addSpaceInline inline = [inline]
 
 -- | This is a tag around a 'String' representing whether the 'String' is Latin
@@ -287,8 +288,8 @@ data CharLang
 -- >>> textLangToInline $ English "foobar"
 -- Span ("",["ascii"],[]) [Str "foobar"]
 textLangToInline :: TextLang -> Inline
-textLangToInline (Japanese string) = Str string
-textLangToInline (English string) = Span ("", ["ascii"], []) [Str string]
+textLangToInline (Japanese string) = Str (Text.pack string)
+textLangToInline (English string) = Span ("", ["ascii"], []) [Str (Text.pack string)]
 
 -- | Split a 'String' into groups of 'TextLang'.
 --
@@ -388,7 +389,7 @@ charLangToTextLang cs@(JapaneseChar{} :| _) =
 charLangToTextLang cs@(EnglishChar{} :| _) =
   English . toList $ charLangToChar <$> cs
 
-getFeedConfig :: MonadMetadata m => Identifier -> m FeedConfiguration
+getFeedConfig :: (MonadMetadata m, MonadFail m) => Identifier -> m FeedConfiguration
 getFeedConfig ident = do
     feedTitle       <- getMetadataField' ident "title"
     feedDescription <- getMetadataField' ident "description"
@@ -407,15 +408,15 @@ data PostSection = PostSection
   } deriving Show
 
 -- | Extract element ID from `Attr`.
-attrId :: Attr -> String
+attrId :: Attr -> Text
 attrId (x, _, _) = x
 
 -- | Construct `Attr` with ID.
-idAttr :: String -> Attr
+idAttr :: Text -> Attr
 idAttr s = (s, [], [])
 
 -- | Construct `Attr` with one class.
-classAttr :: String -> Attr
+classAttr :: Text -> Attr
 classAttr s = ("", [s], [])
 
 -- | Eliminate all links from `Block`s or `Inline`s.
@@ -469,7 +470,7 @@ makeTOCList xs0@(x0 : _) = PB.bulletList $ Tree.foldTree fld <$> unfoldTree_DF u
 
     listItem :: PostSection -> PB.Blocks
     listItem PostSection{..} =
-        PB.plain $ PB.link ("#" ++ attrId psHeaderAttr)
+        PB.plain $ PB.link ("#" <> attrId psHeaderAttr)
                            (attrId psHeaderAttr)
                            (PB.fromList $ elimLink psHeaderInline)
 
@@ -482,7 +483,7 @@ makeSectionBlock PostSection{..} = hd <> PB.fromList psContent
            <> PB.fromList psHeaderInline
 
     anchor = PB.spanWith (classAttr "link-to-here-outer") $
-               PB.link ("#" ++ attrId psHeaderAttr)
+               PB.link ("#" <> attrId psHeaderAttr)
                        (attrId psHeaderAttr) $
                  PB.spanWith (classAttr "link-to-here") $
                    PB.str "Link to" <> PB.linebreak <> PB.str "here"
@@ -505,4 +506,3 @@ postMakeTOC (Pandoc meta blk0) = Pandoc meta (PB.toList processed)
                 PB.divWith (classAttr "table-of-contents-title")
                   (PB.plain $ PB.str "Contents")
                 <> tocList
-
diff --git a/stack.yaml b/stack.yaml
index aa20e6da..e57795a8 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,7 +1,5 @@
 flags: {}
 packages:
 - '.'
-extra-deps:
-- hakyll-4.12.5.1
-- lrucache-1.2.0.1
-resolver: lts-13.11
+extra-deps: []
+resolver: lts-16.25
diff --git a/stack.yaml.lock b/stack.yaml.lock
index a6567e8f..31befa1d 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -3,24 +3,10 @@
 # For more information, please see the documentation at:
 #   https://docs.haskellstack.org/en/stable/lock_files
 
-packages:
-- completed:
-    hackage: hakyll-4.12.5.1@sha256:d1948b265e6628bcb6875571212f9acefe23179c73ca4f87f417b290ff381ca6,8677
-    pantry-tree:
-      size: 7631
-      sha256: ac35d6b2a3b6d87517ff5184430a283c378330ec5da6f7dce26416568bf134ee
-  original:
-    hackage: hakyll-4.12.5.1
-- completed:
-    hackage: lrucache-1.2.0.1@sha256:18fc3d7052012c7ab3cd395160f34b53c5e1ec5379cc45185baf35b90ffadc2e,1254
-    pantry-tree:
-      size: 619
-      sha256: 61b2a39a11873f2d8a577e1f6b5e848d2f465ea7f6837ce15436796d3a20eda0
-  original:
-    hackage: lrucache-1.2.0.1
+packages: []
 snapshots:
 - completed:
-    size: 495801
-    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/13/11.yaml
-    sha256: 835062158db2b3ebb8b9525d9662a02ebf9783e8f6a08a64684cd5546f847152
-  original: lts-13.11
+    size: 533252
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/16/25.yaml
+    sha256: 147598b98bdd95ec0409bac125a4f1bff3cd4f8d73334d283d098f66a4bcc053
+  original: lts-16.25