diff --git a/xmonad-contrib.cabal b/xmonad-contrib.cabal
index 5bf13ef5c4..4fd93927b2 100644
--- a/xmonad-contrib.cabal
+++ b/xmonad-contrib.cabal
@@ -62,6 +62,7 @@ library
                    X11 >= 1.10 && < 1.11,
                    xmonad >= 0.16.99999 && < 0.18,
                    utf8-string
+    default-language: Haskell2010
 
     cpp-options:   -DXMONAD_CONTRIB_VERSION_MAJOR=0
                    -DXMONAD_CONTRIB_VERSION_MINOR=17
@@ -449,6 +450,7 @@ test-suite tests
                , xmonad >= 0.16.9999 && < 0.18
   cpp-options: -DTESTING
   ghc-options: -Wall -Wno-unused-do-bind
+  default-language: Haskell2010
 
   if flag(pedantic)
      ghc-options: -Werror -Wwarn=deprecations