diff --git a/.appveyor.yml b/.appveyor.yml
index a17dd17c..56c063f7 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -1,7 +1,8 @@
 install:
   # Using '-y' and 'refreshenv' as a workaround to:
   # https://github.com/haskell/cabal/issues/3687
-  - choco install -y ghc --version 8.2.1
+  - choco install -y ghc --version 8.4.1
+  - choco install -y cabal --version 2.2.0.0
   - refreshenv
   # See http://help.appveyor.com/discussions/problems/6312-curl-command-not-found#comment_42195491
   # NB: Do this after refreshenv, otherwise it will be clobbered!
diff --git a/.travis.yml b/.travis.yml
index a0c1c61c..0baf6cad 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,12 +10,12 @@ cache:
 
 matrix:
   include:
-    - env: CABALVER="2.0" GHCVER="8.2.1"
-      compiler: ": #GHC 8.2.1"
-      addons: {apt: {packages: [cabal-install-2.0,ghc-8.2.1], sources: [hvr-ghc]}}
+    - env: CABALVER="2.2" GHCVER="8.4.1"
+      compiler: ": #GHC 8.4.1"
+      addons: {apt: {packages: [cabal-install-2.2,ghc-8.4.1], sources: [hvr-ghc]}}
     - os: osx
-      env: CABALVER="2.0" GHCVER="8.2.1"
-      compiler: ": #GHC 8.2.1"
+      env: CABALVER="2.2" GHCVER="8.4.1"
+      compiler: ": #GHC 8.4.1"
 
 before_install:
   - if [[ $TRAVIS_OS_NAME == 'linux' ]];
@@ -36,6 +36,7 @@ before_install:
   - env
 
 script:
+  - cp cabal.GHC84.config cabal.project.freeze
   - cabal update
   - cabal new-build -j
 
diff --git a/cabal.GHC710.config b/cabal.GHC710.config
index 4be14b8b..6849a2ed 100644
--- a/cabal.GHC710.config
+++ b/cabal.GHC710.config
@@ -1822,8 +1822,6 @@ constraints: abstract-deque ==0.3,
              users-persistent ==0.5.0.2,
              users-postgresql-simple ==0.5.0.2,
              users-test ==0.5.0.1,
-             utf8-light ==0.4.2,
-             utf8-string ==1.0.1.1,
              utility-ht ==0.0.12,
              uu-interleaved ==0.2.0.0,
              uu-parsinglib ==2.9.1.1,
diff --git a/cabal.GHC80.config b/cabal.GHC80.config
index 29a639f0..2d99f33e 100644
--- a/cabal.GHC80.config
+++ b/cabal.GHC80.config
@@ -1934,8 +1934,6 @@ constraints: abstract-deque ==0.3,
              users ==0.5.0.0,
              users-postgresql-simple ==0.5.0.2,
              users-test ==0.5.0.1,
-             utf8-light ==0.4.2,
-             utf8-string ==1.0.1.1,
              utility-ht ==0.0.12,
              uu-interleaved ==0.2.0.0,
              uu-parsinglib ==2.9.1.1,
diff --git a/cabal.GHC82.config b/cabal.GHC82.config
index 74b13fd4..e0cf8820 100644
--- a/cabal.GHC82.config
+++ b/cabal.GHC82.config
@@ -121,7 +121,6 @@ constraints: Cabal -bundled-binary-generic,
              transformers-compat +five -four +generic-deriving +mtl -three -two,
              unordered-containers ==0.2.9.0,
              unordered-containers -debug,
-             utf8-string ==1.0.1.1,
              uuid-types ==1.0.3,
              vector ==0.12.0.1,
              vector +boundschecks -internalchecks -unsafechecks -wall,
diff --git a/cabal.GHC84.config b/cabal.GHC84.config
new file mode 100644
index 00000000..c6393af4
--- /dev/null
+++ b/cabal.GHC84.config
@@ -0,0 +1,133 @@
+constraints: Cabal ==2.2.0.0,
+             FloatingHex ==0.4,
+             Glob ==0.9.2,
+             GraphSCC ==1.0.4,
+             GraphSCC -use-maps,
+             HUnit ==1.6.0.0,
+             Only ==0.1,
+             QuickCheck ==2.11.3,
+             QuickCheck +templatehaskell,
+             abstract-deque ==0.3,
+             abstract-deque -usecas,
+             abstract-par ==0.3.3,
+             aeson ==1.3.0.0,
+             aeson -bytestring-builder -cffi -developer -fast,
+             alex ==3.2.4,
+             alex +small_base,
+             ansi-terminal ==0.8.0.2,
+             ansi-terminal -example,
+             ansi-wl-pprint ==0.6.8.2,
+             ansi-wl-pprint -example,
+             array ==0.5.2.0,
+             async ==2.2.1,
+             async -bench,
+             attoparsec ==0.13.2.2,
+             attoparsec -developer,
+             base ==4.11.0.0,
+             base-compat ==0.9.3,
+             base-orphans ==0.7,
+             binary ==0.8.5.1,
+             blaze-builder ==0.4.1.0,
+             blaze-html ==0.9.0.1,
+             blaze-markup ==0.8.2.0,
+             bytestring ==0.10.8.2,
+             call-stack ==0.1.0,
+             cassava ==0.5.1.0,
+             cassava -bytestring--lt-0_10_4,
+             cereal ==0.5.5.0,
+             cereal -bytestring-builder,
+             code-page ==0.1.3,
+             colour ==2.3.4,
+             containers ==0.5.11.0,
+             crackNum ==2.0,
+             criterion ==1.4.0.0,
+             criterion -embed-data-files -fast,
+             cryptol +relocatable -static,
+             cryptol-test-runner -static,
+             data-binary-ieee754 ==0.4.4,
+             deepseq ==1.4.3.0,
+             directory ==1.3.1.5,
+             dlist ==0.8.0.4,
+             erf ==2.0.0.0,
+             exceptions ==0.10.0,
+             extensible-exceptions ==0.1.1.4,
+             filepath ==1.4.2,
+             generic-deriving ==1.12.1,
+             generic-deriving +base-4-9,
+             gitrev ==1.3.1,
+             happy ==1.19.9,
+             happy +small_base,
+             hashable ==1.2.7.0,
+             hashable -examples +integer-gmp +sse2 -sse41,
+             haskeline ==0.7.4.2,
+             heredoc ==0.2.0.0,
+             hostname ==1.0,
+             hsc2hs ==0.68.3,
+             hsc2hs -in-ghc-tree,
+             ieee754 ==0.8.0,
+             integer-logarithms ==1.0.2.1,
+             integer-logarithms -check-bounds +integer-gmp,
+             js-flot ==0.8.3,
+             js-jquery ==3.3.1,
+             math-functions ==0.2.1.0,
+             math-functions -system-expm1,
+             microstache ==1.0.1.1,
+             monad-control ==1.0.2.3,
+             monad-par ==0.3.4.8,
+             monad-par -chaselev -newgeneric,
+             monad-par-extras ==0.3.3,
+             monadLib ==3.7.3,
+             monadLib -base3,
+             mtl ==2.2.2,
+             mwc-random ==0.13.6.0,
+             old-locale ==1.0.0.7,
+             optparse-applicative ==0.14.2.0,
+             parallel ==3.2.1.1,
+             parsec ==3.1.13.0,
+             pretty ==1.1.3.6,
+             primitive ==0.6.3.0,
+             process ==1.6.3.0,
+             random ==1.1,
+             regex-base ==0.93.2,
+             regex-base +newbase +splitbase,
+             regex-posix ==0.95.2,
+             regex-posix +newbase +splitbase,
+             rts ==1.0,
+             sbv ==7.6,
+             scientific ==0.3.5.3,
+             scientific -bytestring-builder -integer-simple,
+             semigroups ==0.18.4,
+             semigroups +binary +bytestring -bytestring-builder +containers +deepseq +hashable +tagged +text +transformers +unordered-containers,
+             simple-smt ==0.7.1,
+             statistics ==0.14.0.2,
+             stm ==2.4.5.0,
+             strict ==0.3.2,
+             strict +split-base,
+             syb ==0.7,
+             tagged ==0.8.5,
+             tagged +deepseq +transformers,
+             terminfo ==0.4.1.1,
+             test-framework ==0.8.2.0,
+             test-framework-hunit ==0.3.0.2,
+             test-framework-hunit -base3 +base4,
+             text ==1.2.3.0,
+             text-short ==0.1.2,
+             text-short -asserts,
+             tf-random ==0.5,
+             th-abstraction ==0.2.6.0,
+             time-locale-compat ==0.1.1.3,
+             time-locale-compat -old-locale,
+             transformers-base ==0.4.5.2,
+             transformers-base +orphaninstances,
+             transformers-compat ==0.6.1.6,
+             transformers-compat -five -four +generic-deriving +mtl -three -two,
+             unordered-containers ==0.2.9.0,
+             unordered-containers -debug,
+             uuid-types ==1.0.3,
+             vector ==0.12.0.1,
+             vector +boundschecks -internalchecks -unsafechecks -wall,
+             vector-algorithms ==0.7.0.1,
+             vector-algorithms -bench +boundschecks -internalchecks +properties -unsafechecks,
+             vector-binary-instances ==0.2.4,
+             vector-th-unbox ==0.2.1.6,
+             xml ==1.3.14