diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # wai-app-static changelog
 
+## 3.1.7.2
+
+* optparse-applicative 0.16.0.0 support
+
 ## 3.1.7.1
 
 * Update the test suite too
diff --git a/Network/Wai/Application/Static.hs b/Network/Wai/Application/Static.hs
--- a/Network/Wai/Application/Static.hs
+++ b/Network/Wai/Application/Static.hs
@@ -164,11 +164,13 @@
             -- Didn't match, but we have a hash value. Send the file contents
             -- with an ETag header.
             --
-            -- Note: It would be arguably better to next check
-            -- if-modified-since and return a 304 if that indicates a match as
-            -- well. However, the circumstances under which such a situation
-            -- could arise would be very anomalous, and should likely warrant a
-            -- new file being sent anyway.
+            -- RFC7232 (HTTP 1.1):
+            -- > A recipient MUST ignore If-Modified-Since if the request contains an
+            -- > If-None-Match header field; the condition in If-None-Match is
+            -- > considered to be a more accurate replacement for the condition in
+            -- > If-Modified-Since, and the two are only combined for the sake of
+            -- > interoperating with older intermediaries that might not implement
+            -- > If-None-Match.
             (Just hash, _) -> respond [("ETag", hash)]
 
             -- No hash value available, fall back to last modified support.
@@ -243,7 +245,7 @@
     response :: StaticResponse -> IO W.ResponseReceived
     response (FileResponse file ch) = do
         mimetype <- ssGetMimeType ss file
-        let filesize = fileGetSize file
+        -- let filesize = fileGetSize file
         let headers = ("Content-Type", mimetype)
                     -- Let Warp provide the content-length, since it takes
                     -- range requests into account
diff --git a/WaiAppStatic/CmdLine.hs b/WaiAppStatic/CmdLine.hs
--- a/WaiAppStatic/CmdLine.hs
+++ b/WaiAppStatic/CmdLine.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE DeriveDataTypeable, RecordWildCards #-}
+{-# LANGUAGE DeriveDataTypeable, RecordWildCards, CPP #-}
 -- | Command line version of wai-app-static, used for the warp-static server.
 module WaiAppStatic.CmdLine
     ( runCommandLine
@@ -39,6 +39,7 @@
     }
 
 #if MIN_VERSION_optparse_applicative(0, 10, 0)
+option' :: Mod OptionFields Int -> Parser Int
 option' = option auto
 #else
 option' = option
@@ -113,5 +114,9 @@
     where
       helperOption :: Parser (a -> a)
       helperOption =
+#if MIN_VERSION_optparse_applicative(0,16,0)
+        abortOption (ShowHelpText Nothing) $
+#else
         abortOption ShowHelpText $
+#endif
         mconcat [long "help", help "Show this help text", hidden]
diff --git a/WaiAppStatic/Listing.hs b/WaiAppStatic/Listing.hs
--- a/WaiAppStatic/Listing.hs
+++ b/WaiAppStatic/Listing.hs
@@ -64,7 +64,7 @@
 
     -- Add a link to the root of the tree
     showFolder' :: Bool -> Pieces -> H.Html
-    showFolder' hasTrailingSlash pieces  = showFolder hasTrailingSlash (unsafeToPiece "root" : pieces)
+    showFolder' hasTrailingSlash pieces' = showFolder hasTrailingSlash (unsafeToPiece "root" : pieces')
 
     showFolder :: Bool -> Pieces -> H.Html
     showFolder _ [] = "/" -- won't happen
diff --git a/WaiAppStatic/Storage/Embedded/TH.hs b/WaiAppStatic/Storage/Embedded/TH.hs
--- a/WaiAppStatic/Storage/Embedded/TH.hs
+++ b/WaiAppStatic/Storage/Embedded/TH.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE TemplateHaskell, QuasiQuotes, OverloadedStrings, MagicHash #-}
+{-# LANGUAGE TemplateHaskell, QuasiQuotes, OverloadedStrings, MagicHash, CPP #-}
 module WaiAppStatic.Storage.Embedded.TH(
     Etag
   , EmbeddableEntry(..)
@@ -7,7 +7,6 @@
 
 import Data.ByteString.Builder.Extra (byteStringInsert)
 import Codec.Compression.GZip (compress)
-import Control.Applicative
 import Data.ByteString.Unsafe (unsafePackAddressLen)
 import Data.Either (lefts, rights)
 import GHC.Exts (Int(..))
diff --git a/WaiAppStatic/Types.hs b/WaiAppStatic/Types.hs
--- a/WaiAppStatic/Types.hs
+++ b/WaiAppStatic/Types.hs
@@ -59,6 +59,8 @@
 toPieces = mapM toPiece
 
 -- | Request coming from a user. Corresponds to @pathInfo@.
+--
+-- The root path is the empty list.
 type Pieces = [Piece]
 
 -- | Values for the max-age component of the cache-control response header.
diff --git a/wai-app-static.cabal b/wai-app-static.cabal
--- a/wai-app-static.cabal
+++ b/wai-app-static.cabal
@@ -1,5 +1,5 @@
 name:            wai-app-static
-version:         3.1.7.1
+version:         3.1.7.2
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>
@@ -8,7 +8,7 @@
 description:     API docs and the README are available at <http://www.stackage.org/package/wai-app-static>.
 category:        Web, Yesod
 stability:       Stable
-cabal-version:   >= 1.8
+cabal-version:   >= 1.10
 build-type:      Simple
 homepage:        http://www.yesodweb.com/book/web-application-interface
 Extra-source-files:
@@ -25,6 +25,7 @@
     Default:       False
 
 library
+    default-language: Haskell2010
     build-depends:   base                      >= 4        && < 5
                    , wai                       >= 3.0      && < 3.3
                    , bytestring                >= 0.10.4
@@ -61,12 +62,12 @@
                      WaiAppStatic.Storage.Embedded.Runtime
                      WaiAppStatic.Storage.Embedded.TH
     ghc-options:     -Wall
-    extensions:     CPP
 
     if flag(print)
       cpp-options:  -DPRINT
 
 Executable warp
+  default-language: Haskell2010
   Main-is:        warp-static.hs
   hs-source-dirs: app
   Build-depends: base            >= 4                  && < 5
@@ -78,6 +79,7 @@
                , mime-types      >= 0.1                && < 0.2
 
 test-suite runtests
+    default-language: Haskell2010
     hs-source-dirs: test
     main-is: ../tests.hs
     type: exitcode-stdio-1.0