diff --git a/.travis.yml b/.travis.yml
index b2c5cb0..7180ce5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -10,33 +10,37 @@ cache:
 # cache file per set of arguments.
 matrix:
   include:
-  - env: ARGS="--resolver lts-7"
+  - env: ARGS="--stack-yaml=stack.ghc-8.4.yaml --resolver lts-7"
     compiler: ": #stack 8.0.1"
     addons: { apt: { packages: [libgmp-dev] } }
 
-  - env: ARGS="--resolver lts-8"
+  - env: ARGS="--stack-yaml=stack.ghc-8.4.yaml --resolver lts-8"
     compiler: ": #stack 8.0.2"
     addons: { apt: { packages: [libgmp-dev] } }
 
-  - env: ARGS="--resolver lts-10"
+  - env: ARGS="--stack-yaml=stack.ghc-8.4.yaml --resolver lts-10"
     compiler: ": #stack 8.2.1"
     addons: { apt: { packages: [libgmp-dev] } }
 
-  - env: ARGS="--resolver lts-11"
+  - env: ARGS="--stack-yaml=stack.ghc-8.4.yaml --resolver lts-11"
     compiler: ": #stack 8.2.2"
     addons: { apt: { packages: [libgmp-dev] } }
 
-  - env: ARGS="--resolver lts-12"
+  - env: ARGS="--stack-yaml=stack.ghc-8.4.yaml --resolver lts-12"
     compiler: ": #stack 8.4.4"
     addons: { apt: { packages: [libgmp-dev] } }
 
-  - env: ARGS="--resolver nightly"
+  - env: ARGS="--resolver lts-14"
+    compiler: ": #stack 8.6.5"
+    addons: { apt: { packages: [libgmp-dev] } }
+
+  - env: ARGS="--stack-yaml=stack.ghc-8.8.yaml --resolver nightly"
     compiler: ": #stack nightly"
     addons: { apt: { packages: [libgmp-dev] } }
 
   allow_failures:
   # Nightly builds are allowed to fail
-  - env: ARGS="--resolver nightly"
+  - env: ARGS="--stack-yaml=stack.ghc-8.8.yaml --resolver nightly"
 
 before_install:
 # Using compiler above sets CC to an invalid value, so unset it
diff --git a/examples/src/Trace.hs b/examples/src/Trace.hs
index 63e6b1c..9f8b80b 100644
--- a/examples/src/Trace.hs
+++ b/examples/src/Trace.hs
@@ -1,13 +1,11 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE NoMonomorphismRestriction #-}
 
 module Trace (module Trace) where
 
-import Control.Applicative ((<$>), (<*>), pure)
-import Data.Function (($))
-import Data.Int (Int)
+#if !MIN_VERSION_base(4,11,0)
 import Data.Monoid ((<>))
-import System.IO (IO)
-import Text.Show (Show(show))
+#endif
 
 import Control.Monad.Freer (Eff, Member)
 import Control.Monad.Freer.Reader (ask, runReader)
diff --git a/package.yaml b/package.yaml
index 890fef3..cd8b445 100644
--- a/package.yaml
+++ b/package.yaml
@@ -57,7 +57,7 @@ library:
   dependencies:
   - natural-transformation >= 0.2
   - transformers-base
-  - template-haskell >= 2.11 && < 2.15
+  - template-haskell >= 2.11 && < 2.16
 
 executables:
   freer-examples:
diff --git a/src/Control/Monad/Freer/Writer.hs b/src/Control/Monad/Freer/Writer.hs
index 604660d..45a0012 100644
--- a/src/Control/Monad/Freer/Writer.hs
+++ b/src/Control/Monad/Freer/Writer.hs
@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 -- |
 -- Module:       Control.Monad.Freer.Writer
 -- Description:  Composable Writer effects.
@@ -19,7 +21,10 @@ module Control.Monad.Freer.Writer
   ) where
 
 import Control.Arrow (second)
+
+#if !MIN_VERSION_base(4,11,0)
 import Data.Monoid ((<>))
+#endif
 
 import Control.Monad.Freer.Internal (Eff, Member, handleRelay, send)
 
diff --git a/src/Data/OpenUnion/Internal.hs b/src/Data/OpenUnion/Internal.hs
index b9bc4d6..2781ab9 100644
--- a/src/Data/OpenUnion/Internal.hs
+++ b/src/Data/OpenUnion/Internal.hs
@@ -32,11 +32,12 @@
 -- substitution for @Typeable@.
 module Data.OpenUnion.Internal where
 
+import Data.Kind (Type)
 import GHC.TypeLits (TypeError, ErrorMessage(..))
 import Unsafe.Coerce (unsafeCoerce)
 
 -- | Open union is a strong sum (existential with an evidence).
-data Union (r :: [* -> *]) a where
+data Union (r :: [Type -> Type]) a where
   Union :: {-# UNPACK #-} !Word -> t a -> Union r a
 
 -- | Takes a request of type @t :: * -> *@, and injects it into the 'Union'.
@@ -76,7 +77,7 @@ newtype P t r = P {unP :: Word}
 -- prior to recursion, and it is used to produce better type errors.
 --
 -- This is essentially a compile-time computation without run-time overhead.
-class FindElem (t :: * -> *) (r :: [* -> *]) where
+class FindElem (t :: Type -> Type) (r :: [Type -> Type]) where
   -- | Position of the element @t :: * -> *@ in a type list @r :: [* -> *]@.
   --
   -- Position is computed during compilation, i.e. there is no run-time
@@ -96,7 +97,7 @@ instance {-# OVERLAPPABLE #-} FindElem t r => FindElem t (t' ': r) where
 
 -- | Instance resolution for this class fails with a custom type error
 -- if @t :: * -> *@ is not in the list @r :: [* -> *]@.
-class IfNotFound (t :: * -> *) (r :: [* -> *]) (w :: [* -> *])
+class IfNotFound (t :: Type -> Type) (r :: [Type -> Type]) (w :: [Type -> Type])
 
 -- | If we reach an empty list, that’s a failure, since it means the type isn’t
 -- in the list. For GHC >=8, we can render a custom type error that explicitly
@@ -128,7 +129,7 @@ instance {-# INCOHERENT #-} IfNotFound t r w
 -- @
 -- 'Member' ('Control.Monad.Freer.State.State' 'Integer') effs => 'Control.Monad.Freer.Eff' effs ()
 -- @
-class FindElem eff effs => Member (eff :: * -> *) effs where
+class FindElem eff effs => Member (eff :: Type -> Type) effs where
   -- This type class is used for two following purposes:
   --
   -- * As a @Constraint@ it guarantees that @t :: * -> *@ is a member of a
diff --git a/stack.ghc-8.4.yaml b/stack.ghc-8.4.yaml
new file mode 100644
index 0000000..66e1922
--- /dev/null
+++ b/stack.ghc-8.4.yaml
@@ -0,0 +1,4 @@
+resolver: lts-12.26
+packages: [.]
+extra-deps:
+- extensible-effects-3.1.0.0
diff --git a/stack.ghc-8.8.yaml b/stack.ghc-8.8.yaml
new file mode 100644
index 0000000..c91969a
--- /dev/null
+++ b/stack.ghc-8.8.yaml
@@ -0,0 +1,3 @@
+resolver: nightly-2019-10-04
+packages: [.]
+extra-deps: []
diff --git a/stack.yaml b/stack.yaml
index ee19644..e04f6cc 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1,10 +1,4 @@
-resolver: lts-12.18
-
-packages:
-- '.'
-
+resolver: lts-14.7
+packages: [.]
 extra-deps:
-- extensible-effects-3.1.0.0
-
-flags: {}
-extra-package-dbs: []
+- extensible-effects-5.0.0.1@sha256:2ed0bee04c8bf334358147da6d92ff31e9fbbefceb75ef3e408a0d858aec0cc6,9013
diff --git a/stack.yaml.lock b/stack.yaml.lock
new file mode 100644
index 0000000..035a407
--- /dev/null
+++ b/stack.yaml.lock
@@ -0,0 +1,19 @@
+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/lock_files
+
+packages:
+- completed:
+    hackage: extensible-effects-5.0.0.1@sha256:2ed0bee04c8bf334358147da6d92ff31e9fbbefceb75ef3e408a0d858aec0cc6,9013
+    pantry-tree:
+      size: 3306
+      sha256: 4c520f1ccb76ed1d304cb5967e6679e31c907d3c0ba5d7e4a459e827b9a08173
+  original:
+    hackage: extensible-effects-5.0.0.1@sha256:2ed0bee04c8bf334358147da6d92ff31e9fbbefceb75ef3e408a0d858aec0cc6,9013
+snapshots:
+- completed:
+    size: 523700
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/14/7.yaml
+    sha256: 8e3f3c894be74d71fa4bf085e0a8baae7e4d7622d07ea31a52736b80f8b9bb1a
+  original: lts-14.7