diff --git a/semantic-ast/src/Main.hs b/semantic-ast/src/Main.hs
index 6d8f70552..5059504d3 100644
--- a/semantic-ast/src/Main.hs
+++ b/semantic-ast/src/Main.hs
@@ -69,4 +69,5 @@ opts = info (parseAST <**> helper)
 -- TODO: Define formats for json, sexpression, etc.
 data Format = Show
             | Pretty
+            | Json
   deriving (Read)