diff --git a/app/Main.hs b/app/Main.hs
index 6c1c01c75e31cf95b9102800f7e4e567500b39e9..c7fc8b3c6daa544b38c4a2c87f9c57c194239b0c 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -61,6 +61,7 @@ cliParser :: Parser CliOptions
 cliParser = CliOptions 
   <$> flag untyped systemf (long "system-f" <> 
                             short 'f' <> 
+                            internal <>    -- this is a secret feature
                             help "Use the System F interpreter")
 
   <*> switch (long "version" <>