diff --git a/src/Semantic/IO.hs b/src/Semantic/IO.hs
index 602bfb75e..69525661f 100644
--- a/src/Semantic/IO.hs
+++ b/src/Semantic/IO.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE DeriveAnyClass, DuplicateRecordFields, GADTs, ScopedTypeVariables, TupleSections, TypeOperators, UndecidableInstances #-}
+{-# LANGUAGE DeriveAnyClass, DeriveDataTypeable, DuplicateRecordFields, GADTs, ScopedTypeVariables, TupleSections, TypeOperators, UndecidableInstances #-}
 module Semantic.IO
 ( readFile
 , readFilePair