diff --git a/.travis.yml b/.travis.yml
index 8b2d437..09ca57d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,6 @@
 # This Travis job script has been generated by a script via
 #
-#   make_travis_yml_2.hs '-o' '.travis.yml' '--irc-channel=irc.freenode.org#clash-lang' 'ghc-tcplugins-extra.cabal'
+#   runghc make_travis_yml_2.hs '-o' '.travis.yml' '--irc-channel=irc.freenode.org#clash-lang' 'ghc-tcplugins-extra.cabal'
 #
 # For more information, see https://github.com/hvr/multi-ghc-travis
 #
@@ -32,7 +32,7 @@ before_cache:
   - rm -fv $HOME/.cabal/packages/hackage.haskell.org/01-index.tar
   - rm -fv $HOME/.cabal/packages/hackage.haskell.org/01-index.tar.idx
 
-  - rm -fv $HOME/.cabal/packages/head.hackage
+  - rm -rfv $HOME/.cabal/packages/head.hackage
 
 matrix:
   include:
@@ -46,17 +46,24 @@ matrix:
     # env: TEST=--disable-tests BENCH=--disable-benchmarks
       addons: {apt: {packages: [ghc-ppa-tools,cabal-install-head,ghc-8.2.2], sources: [hvr-ghc]}}
     - compiler: "ghc-8.4.1"
-      env: GHCHEAD=true
+    # env: TEST=--disable-tests BENCH=--disable-benchmarks
       addons: {apt: {packages: [ghc-ppa-tools,cabal-install-head,ghc-8.4.1], sources: [hvr-ghc]}}
+    - compiler: "ghc-head"
+      env: GHCHEAD=true
+      addons: {apt: {packages: [ghc-ppa-tools,cabal-install-head,ghc-head], sources: [hvr-ghc]}}
 
   allow_failures:
-    - compiler: "ghc-8.4.1"
+    - compiler: "ghc-head"
 
 before_install:
   - HC=${CC}
   - HCPKG=${HC/ghc/ghc-pkg}
   - unset CC
-  - "PATH=/opt/ghc/bin:/opt/ghc-ppa-tools/bin:$PATH"
+  - ROOTDIR=$(pwd)
+  - mkdir -p $HOME/.local/bin
+  - "PATH=/opt/ghc/bin:/opt/ghc-ppa-tools/bin:$HOME/local/bin:$PATH"
+  - HCNUMVER=$(( $(${HC} --numeric-version|sed -E 's/([0-9]+)\.([0-9]+)\.([0-9]+).*/\1 * 10000 + \2 * 100 + \3/') ))
+  - echo $HCNUMVER
 
 install:
   - cabal --version
@@ -68,29 +75,32 @@ install:
   - GHCHEAD=${GHCHEAD-false}
   - travis_retry cabal update -v
   - "sed -i.bak 's/^jobs:/-- jobs:/' ${HOME}/.cabal/config"
-  - rm -fv cabal.project.local
-  - "printf 'packages: \".\"\\n' > cabal.project"
+  - rm -fv cabal.project cabal.project.local
   # Overlay Hackage Package Index for GHC HEAD: https://github.com/hvr/head.hackage
   - |
     if $GHCHEAD; then
-      echo 'allow-newer: *:base, *:template-haskell' >> cabal.project
-      echo 'repository head.hackage' >> cabal.project
-      echo '   url: http://head.hackage.haskell.org/' >> cabal.project
-      echo '   secure: True' >> cabal.project
-      echo '   root-keys: 07c59cb65787dedfaef5bd5f987ceb5f7e5ebf88b904bbd4c5cbdeb2ff71b740' >> cabal.project
-      echo '              2e8555dde16ebd8df076f1a8ef13b8f14c66bad8eafefd7d9e37d0ed711821fb' >> cabal.project
-      echo '              8f79fd2389ab2967354407ec852cbe73f2e8635793ac446d09461ffb99527f6e' >> cabal.project
-      echo '   key-threshold: 3' >> cabal.project
+      sed -i.bak 's/-- allow-newer:.*/allow-newer: *:base, *:template-haskell, *:ghc, *:Cabal/' ${HOME}/.cabal/config
+
+      echo 'repository head.hackage'                                                        >> ${HOME}/.cabal/config
+      echo '   url: http://head.hackage.haskell.org/'                                       >> ${HOME}/.cabal/config
+      echo '   secure: True'                                                                >> ${HOME}/.cabal/config
+      echo '   root-keys: 07c59cb65787dedfaef5bd5f987ceb5f7e5ebf88b904bbd4c5cbdeb2ff71b740' >> ${HOME}/.cabal/config
+      echo '              2e8555dde16ebd8df076f1a8ef13b8f14c66bad8eafefd7d9e37d0ed711821fb' >> ${HOME}/.cabal/config
+      echo '              8f79fd2389ab2967354407ec852cbe73f2e8635793ac446d09461ffb99527f6e' >> ${HOME}/.cabal/config
+      echo '   key-threshold: 3'                                                            >> ${HOME}/.cabal.config
+
+      cabal new-update head.hackage -v
     fi
+  - grep -Ev -- '^\s*--' ${HOME}/.cabal/config | grep -Ev '^\s*$'
+  - "printf 'packages: \".\"\\n' > cabal.project"
   - cat cabal.project
-  - if $GHCHEAD; then cabal new-update head.hackage -v; fi
   - if [ -f "./configure.ac" ]; then
-      (cd "."; autoreconf -i);
+      (cd "." && autoreconf -i);
     fi
   - rm -f cabal.project.freeze
   - cabal new-build -w ${HC} ${TEST} ${BENCH} --project-file="cabal.project" --dep -j2 all
   - cabal new-build -w ${HC} --disable-tests --disable-benchmarks --project-file="cabal.project" --dep -j2 all
-  - rm -rf "."/.ghc.environment.* "."/dist
+  - rm -rf .ghc.environment.* "."/dist
   - DISTDIR=$(mktemp -d /tmp/dist-test.XXXX)
 
 # Here starts the actual work to be performed for the package under test;
@@ -102,18 +112,6 @@ script:
   - cd ${DISTDIR} || false
   - find . -maxdepth 1 -name '*.tar.gz' -exec tar -xvf '{}' \;
   - "printf 'packages: ghc-tcplugins-extra-*/*.cabal\\n' > cabal.project"
-  # Overlay Hackage Package Index for GHC HEAD: https://github.com/hvr/head.hackage
-  - |
-    if $GHCHEAD; then
-      echo 'allow-newer: *:base, *:template-haskell' >> cabal.project
-      echo 'repository head.hackage' >> cabal.project
-      echo '   url: http://head.hackage.haskell.org/' >> cabal.project
-      echo '   secure: True' >> cabal.project
-      echo '   root-keys: 07c59cb65787dedfaef5bd5f987ceb5f7e5ebf88b904bbd4c5cbdeb2ff71b740' >> cabal.project
-      echo '              2e8555dde16ebd8df076f1a8ef13b8f14c66bad8eafefd7d9e37d0ed711821fb' >> cabal.project
-      echo '              8f79fd2389ab2967354407ec852cbe73f2e8635793ac446d09461ffb99527f6e' >> cabal.project
-      echo '   key-threshold: 3' >> cabal.project
-    fi
   - cat cabal.project
   # this builds all libraries and executables (without tests/benchmarks)
   - cabal new-build -w ${HC} --disable-tests --disable-benchmarks all
@@ -124,9 +122,12 @@ script:
   # build & run tests, build benchmarks
   - cabal new-build -w ${HC} ${TEST} ${BENCH} all
 
+  # cabal check
+  - (cd ghc-tcplugins-extra-* && cabal check)
+
   # haddock
   - rm -rf ./dist-newstyle
-  - if $HADDOCK; then cabal new-haddock -w ${HC} --disable-tests --disable-benchmarks all; else echo "Skipping haddock generation";fi
+  - if $HADDOCK; then cabal new-haddock -w ${HC} ${TEST} ${BENCH} all; else echo "Skipping haddock generation";fi
 
 # REGENDATA ["-o",".travis.yml","--irc-channel=irc.freenode.org#clash-lang","ghc-tcplugins-extra.cabal"]
 # EOF
diff --git a/ghc-tcplugins-extra.cabal b/ghc-tcplugins-extra.cabal
index 311a784..c5e1ab6 100644
--- a/ghc-tcplugins-extra.cabal
+++ b/ghc-tcplugins-extra.cabal
@@ -17,7 +17,8 @@ build-type:          Simple
 extra-source-files:  README.md
                      CHANGELOG.md
 cabal-version:       >=1.10
-tested-with:         GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.1
+tested-with:         GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.1,
+                     GHC == 8.5
 
 source-repository head
   type: git