diff --git a/Types.hs b/Types.hs
index 74bfec3..6e83304 100644
--- a/Types.hs
+++ b/Types.hs
@@ -142,7 +142,7 @@ siteOptions' = do
     value "list.html" <> showDefault
   _timestampSuffix <-
     strOption $
-    long "timestamp-prefix" <>
+    long "timestamp-suffix" <>
     help "Timestamp file suffix for markdowns" <>
     value ".timestamp" <> showDefault
   _extraMeta <-