diff --git a/wai-logger.cabal b/wai-logger.cabal
--- a/wai-logger.cabal
+++ b/wai-logger.cabal
@@ -1,5 +1,5 @@
 Name:                   wai-logger
-Version:                2.3.4
+Version:                2.3.5
 Author:                 Kazu Yamamoto <kazu@iij.ad.jp>
 Maintainer:             Kazu Yamamoto <kazu@iij.ad.jp>
 License:                BSD3
@@ -28,6 +28,8 @@
                       , http-types
                       , network
                       , wai >= 2.0.0
+ if impl(ghc >= 8)
+      Default-Extensions:  Strict StrictData
 
 Test-Suite doctests
   Type:                 exitcode-stdio-1.0
@@ -38,6 +40,8 @@
   Build-Depends:        base
                       , wai-logger
                       , doctest >= 0.10.1
+  if impl(ghc >= 8)
+      Default-Extensions:  Strict StrictData
 
 Source-Repository head
   Type:                 git