diff --git a/iri.cabal b/iri.cabal
index 23f48d5..6fef9c6 100644
--- a/iri.cabal
+++ b/iri.cabal
@@ -123,6 +123,7 @@ library
 
 library punycode
   hs-source-dirs:  punycode
+  default-language:   Haskell2010
   build-depends:
     , base
     , bytestring >=0.10 && <0.13