diff --git a/doc/tutorial/tutorial.cabal b/doc/tutorial/tutorial.cabal
index 021f1a10..badde620 100644
--- a/doc/tutorial/tutorial.cabal
+++ b/doc/tutorial/tutorial.cabal
@@ -46,15 +46,11 @@ library
                      , markdown-unlit >= 0.4
                      , http-client
   default-language:    Haskell2010
-  ghc-options:         -Wall -Werror -pgmL markdown-unlit
-  -- to silence aeson-0.10 warnings:
-  ghc-options:         -fno-warn-missing-methods
-  ghc-options:         -fno-warn-name-shadowing
+  ghc-options:         -Wall -pgmL markdown-unlit
 
 test-suite spec
   type: exitcode-stdio-1.0
-  ghc-options:
-    -Wall -fno-warn-name-shadowing -fno-warn-missing-signatures
+  ghc-options: -Wall
   default-language: Haskell2010
   hs-source-dirs: test
   main-is: Spec.hs
diff --git a/servant-blaze/servant-blaze.cabal b/servant-blaze/servant-blaze.cabal
index 3ce7faa4..c4203651 100644
--- a/servant-blaze/servant-blaze.cabal
+++ b/servant-blaze/servant-blaze.cabal
@@ -31,3 +31,4 @@ library
   hs-source-dirs:      src
   default-language:    Haskell2010
   include-dirs: include
+  ghc-options: -Wall
diff --git a/servant-cassava/servant-cassava.cabal b/servant-cassava/servant-cassava.cabal
index 117ec804..a336c4e8 100644
--- a/servant-cassava/servant-cassava.cabal
+++ b/servant-cassava/servant-cassava.cabal
@@ -28,3 +28,4 @@ library
   hs-source-dirs:      src
   default-language:    Haskell2010
   include-dirs: include
+  ghc-options: -Wall
diff --git a/servant-client/servant-client.cabal b/servant-client/servant-client.cabal
index d074c1f8..a1e42925 100644
--- a/servant-client/servant-client.cabal
+++ b/servant-client/servant-client.cabal
@@ -60,8 +60,7 @@ library
 
 test-suite spec
   type: exitcode-stdio-1.0
-  ghc-options:
-    -Wall -fno-warn-name-shadowing -fno-warn-missing-signatures
+  ghc-options: -Wall
   default-language: Haskell2010
   hs-source-dirs: test
   main-is: Spec.hs
diff --git a/servant-client/test/Servant/ClientSpec.hs b/servant-client/test/Servant/ClientSpec.hs
index 17048593..c41b4093 100644
--- a/servant-client/test/Servant/ClientSpec.hs
+++ b/servant-client/test/Servant/ClientSpec.hs
@@ -28,7 +28,7 @@ import           Control.Applicative        ((<$>))
 import           Control.Arrow              (left)
 import           Control.Concurrent         (forkIO, killThread, ThreadId)
 import           Control.Exception          (bracket)
-import           Control.Monad.Trans.Except (ExceptT, throwE, runExceptT)
+import           Control.Monad.Trans.Except (throwE, runExceptT)
 import           Data.Aeson
 import qualified Data.ByteString.Lazy       as BS
 import           Data.Char                  (chr, isPrint)
diff --git a/servant-docs/servant-docs.cabal b/servant-docs/servant-docs.cabal
index 0c877c52..8ae8b810 100644
--- a/servant-docs/servant-docs.cabal
+++ b/servant-docs/servant-docs.cabal
@@ -82,4 +82,3 @@ test-suite spec
     , servant-docs
     , string-conversions
   default-language: Haskell2010
-
diff --git a/servant-foreign/src/Servant/Foreign/Internal.hs b/servant-foreign/src/Servant/Foreign/Internal.hs
index 72f24116..4e457897 100644
--- a/servant-foreign/src/Servant/Foreign/Internal.hs
+++ b/servant-foreign/src/Servant/Foreign/Internal.hs
@@ -7,7 +7,8 @@
 -- arbitrary programming languages.
 module Servant.Foreign.Internal where
 
-import           Control.Lens hiding (cons, List)
+import           Control.Lens (makePrisms, makeLenses, Getter, (&), (<>~), (%~),
+                               (.~))
 #if !MIN_VERSION_base(4,8,0)
 import           Data.Monoid
 #endif
diff --git a/servant-js/servant-js.cabal b/servant-js/servant-js.cabal
index 52216a1b..13beb73c 100644
--- a/servant-js/servant-js.cabal
+++ b/servant-js/servant-js.cabal
@@ -55,7 +55,7 @@ library
 
 executable counter
   main-is: counter.hs
-  ghc-options: -O2 -Wall
+  ghc-options: -Wall
   hs-source-dirs: examples
 
   if flag(example)
diff --git a/servant-js/src/Servant/JS/Internal.hs b/servant-js/src/Servant/JS/Internal.hs
index d123ef9a..1eb28199 100644
--- a/servant-js/src/Servant/JS/Internal.hs
+++ b/servant-js/src/Servant/JS/Internal.hs
@@ -46,7 +46,7 @@ module Servant.JS.Internal
   , Header
   ) where
 
-import           Control.Lens hiding (List)
+import           Control.Lens ((^.))
 import qualified Data.CharSet as Set
 import qualified Data.CharSet.Unicode.Category as Set
 import           Data.Monoid
diff --git a/servant-lucid/servant-lucid.cabal b/servant-lucid/servant-lucid.cabal
index b0e17a96..5b2199aa 100644
--- a/servant-lucid/servant-lucid.cabal
+++ b/servant-lucid/servant-lucid.cabal
@@ -31,3 +31,4 @@ library
   hs-source-dirs:      src
   default-language:    Haskell2010
   include-dirs: include
+  ghc-options: -Wall
diff --git a/servant-mock/example/main.hs b/servant-mock/example/main.hs
index 4a457467..a602dc88 100644
--- a/servant-mock/example/main.hs
+++ b/servant-mock/example/main.hs
@@ -2,6 +2,9 @@
 {-# LANGUAGE DeriveGeneric              #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE TypeOperators              #-}
+
+{-# OPTIONS_GHC -fno-warn-unused-binds #-}
+
 import           Data.Aeson
 import           GHC.Generics
 import           Network.Wai.Handler.Warp
diff --git a/servant-mock/servant-mock.cabal b/servant-mock/servant-mock.cabal
index 871c3fe9..8940e7c2 100644
--- a/servant-mock/servant-mock.cabal
+++ b/servant-mock/servant-mock.cabal
@@ -35,6 +35,7 @@ library
   hs-source-dirs:      src
   default-language:    Haskell2010
   include-dirs: include
+  ghc-options: -Wall
 
 executable mock-app
   main-is: main.hs
@@ -45,11 +46,11 @@ executable mock-app
     buildable: True
   else
     buildable: False
+  ghc-options: -Wall
 
 test-suite spec
   type: exitcode-stdio-1.0
-  ghc-options:
-    -Wall -fno-warn-name-shadowing
+  ghc-options: -Wall
   default-language: Haskell2010
   hs-source-dirs: test
   main-is: Spec.hs
diff --git a/servant-server/servant-server.cabal b/servant-server/servant-server.cabal
index fc577514..321750db 100644
--- a/servant-server/servant-server.cabal
+++ b/servant-server/servant-server.cabal
@@ -94,8 +94,7 @@ executable greet
 
 test-suite spec
   type: exitcode-stdio-1.0
-  ghc-options:
-    -Wall -fno-warn-name-shadowing -fno-warn-missing-signatures
+  ghc-options: -Wall
   default-language: Haskell2010
   hs-source-dirs: test
   main-is: Spec.hs
@@ -147,5 +146,5 @@ test-suite doctests
  main-is: test/Doctests.hs
  buildable: True
  default-language: Haskell2010
- ghc-options: -threaded
+ ghc-options: -Wall -threaded
  include-dirs: include
diff --git a/servant-server/test/Servant/Server/Internal/ContextSpec.hs b/servant-server/test/Servant/Server/Internal/ContextSpec.hs
index dfac1e2e..887f7269 100644
--- a/servant-server/test/Servant/Server/Internal/ContextSpec.hs
+++ b/servant-server/test/Servant/Server/Internal/ContextSpec.hs
@@ -1,9 +1,9 @@
 {-# LANGUAGE DataKinds #-}
-{-# OPTIONS_GHC -fdefer-type-errors #-}
+{-# OPTIONS_GHC -fdefer-type-errors -Wwarn #-}
 module Servant.Server.Internal.ContextSpec (spec) where
 
 import           Data.Proxy                     (Proxy (..))
-import           Test.Hspec                     (Spec, describe, it, shouldBe, pending, context)
+import           Test.Hspec                     (Spec, describe, it, shouldBe, context)
 import           Test.ShouldNotTypecheck        (shouldNotTypecheck)
 
 import           Servant.API
@@ -26,16 +26,17 @@ spec = do
       shouldNotTypecheck x
 
     context "Show instance" $ do
-      let cxt = 'a' :. True :. EmptyContext
       it "has a Show instance" $ do
+        let cxt = 'a' :. True :. EmptyContext
         show cxt `shouldBe` "'a' :. True :. EmptyContext"
 
       context "bracketing" $ do
         it "works" $ do
+          let cxt = 'a' :. True :. EmptyContext
           show (Just cxt) `shouldBe` "Just ('a' :. True :. EmptyContext)"
 
         it "works with operators" $ do
-          let cxt = (1 :. 'a' :. EmptyContext) :<|> ('b' :. True :. EmptyContext)
+          let cxt = ((1 :: Integer) :. 'a' :. EmptyContext) :<|> ('b' :. True :. EmptyContext)
           show cxt `shouldBe` "(1 :. 'a' :. EmptyContext) :<|> ('b' :. True :. EmptyContext)"
 
   describe "descendIntoNamedContext" $ do
diff --git a/servant-server/test/Servant/Server/Internal/EnterSpec.hs b/servant-server/test/Servant/Server/Internal/EnterSpec.hs
index 1591e987..821d5640 100644
--- a/servant-server/test/Servant/Server/Internal/EnterSpec.hs
+++ b/servant-server/test/Servant/Server/Internal/EnterSpec.hs
@@ -5,7 +5,6 @@ module Servant.Server.Internal.EnterSpec where
 
 import qualified Control.Category           as C
 import           Control.Monad.Reader
-import           Control.Monad.Trans.Except
 import           Data.Proxy
 import           Servant.API
 import           Servant.Server
diff --git a/servant-server/test/Servant/Server/RouterSpec.hs b/servant-server/test/Servant/Server/RouterSpec.hs
index 684361b2..e1ec5d7b 100644
--- a/servant-server/test/Servant/Server/RouterSpec.hs
+++ b/servant-server/test/Servant/Server/RouterSpec.hs
@@ -16,6 +16,7 @@ import           Servant.API
 import           Servant.Server
 import           Servant.Server.Internal
 
+spec :: Spec
 spec = describe "Servant.Server.Internal.Router" $ do
   routerSpec
   distributivitySpec
diff --git a/servant-server/test/Servant/Server/StreamingSpec.hs b/servant-server/test/Servant/Server/StreamingSpec.hs
index ed289257..215664ee 100644
--- a/servant-server/test/Servant/Server/StreamingSpec.hs
+++ b/servant-server/test/Servant/Server/StreamingSpec.hs
@@ -11,7 +11,6 @@ module Servant.Server.StreamingSpec where
 import           Control.Concurrent
 import           Control.Exception hiding (Handler)
 import           Control.Monad.IO.Class
-import           Control.Monad.Trans.Except
 import qualified Data.ByteString as Strict
 import qualified Data.ByteString.Lazy as Lazy
 import           Network.HTTP.Types
diff --git a/servant-server/test/Servant/Server/UsingContextSpec.hs b/servant-server/test/Servant/Server/UsingContextSpec.hs
index 1f9c3328..91ab8376 100644
--- a/servant-server/test/Servant/Server/UsingContextSpec.hs
+++ b/servant-server/test/Servant/Server/UsingContextSpec.hs
@@ -5,7 +5,6 @@
 
 module Servant.Server.UsingContextSpec where
 
-import           Control.Monad.Trans.Except
 import           Network.Wai
 import           Test.Hspec (Spec, describe, it)
 import           Test.Hspec.Wai
diff --git a/servant-server/test/Servant/Server/UsingContextSpec/TestCombinators.hs b/servant-server/test/Servant/Server/UsingContextSpec/TestCombinators.hs
index 21999451..0a718788 100644
--- a/servant-server/test/Servant/Server/UsingContextSpec/TestCombinators.hs
+++ b/servant-server/test/Servant/Server/UsingContextSpec/TestCombinators.hs
@@ -30,12 +30,12 @@ instance (HasContextEntry context String, HasServer subApi context) =>
     String -> ServerT subApi m
 
   route Proxy context delayed =
-    route subProxy context (fmap (inject context) delayed)
+    route subProxy context (fmap inject delayed)
     where
       subProxy :: Proxy subApi
       subProxy = Proxy
 
-      inject context f = f (getContextEntry context)
+      inject f = f (getContextEntry context)
 
 data InjectIntoContext
 
diff --git a/servant/servant.cabal b/servant/servant.cabal
index 1faddaaa..7e0a16f7 100644
--- a/servant/servant.cabal
+++ b/servant/servant.cabal
@@ -89,8 +89,7 @@ library
 
 test-suite spec
   type: exitcode-stdio-1.0
-  ghc-options:
-    -Wall -fno-warn-name-shadowing -fno-warn-missing-signatures
+  ghc-options: -Wall
   default-language: Haskell2010
   hs-source-dirs: test
   main-is: Spec.hs
@@ -122,5 +121,5 @@ test-suite doctests
  main-is: test/Doctests.hs
  buildable: True
  default-language: Haskell2010
- ghc-options: -threaded
+ ghc-options: -Wall -threaded
  include-dirs: include
diff --git a/travis.sh b/travis.sh
index 60734911..cd815efb 100755
--- a/travis.sh
+++ b/travis.sh
@@ -6,7 +6,7 @@ for package in $(cat sources.txt) doc/tutorial ; do
   echo testing $package
   pushd $package
   tinc
-  cabal configure --enable-tests --disable-optimization
+  cabal configure --enable-tests --disable-optimization --ghc-options='-Werror'
   cabal build
   cabal test
   popd