diff --git a/src/Text/Pandoc/Writers/EPUB.hs b/src/Text/Pandoc/Writers/EPUB.hs
index d139c010c..a817f07a5 100644
--- a/src/Text/Pandoc/Writers/EPUB.hs
+++ b/src/Text/Pandoc/Writers/EPUB.hs
@@ -120,7 +120,7 @@ writeEPUB mbStylesheet opts doc@(Pandoc meta _) = do
   let chapterEntries = zipWith chapterToEntry [1..] chapters
 
   -- contents.opf
-  lang <- catch (liftM (takeWhile (/='.')) $ getEnv "lang")
+  lang <- catch (liftM (takeWhile (/='.')) $ getEnv "LANG")
                 (\_ -> return "en-US")
   uuid <- getRandomUUID
   let chapterNode ent = unode "item" !