diff --git a/emacs-lisp/tempel_templates.org b/emacs-lisp/tempel_templates.org
index 4a714ec..512e8bf 100644
--- a/emacs-lisp/tempel_templates.org
+++ b/emacs-lisp/tempel_templates.org
@@ -222,4 +222,6 @@
        (s fname) " " (p "pattern") " = " (p "undefined"))
   ; guarded fn
   (<- (p "x") " <- " (p "undefined"))
+  (aeson "instance A.ToJSON " (p "" type) " where" n
+         "instance A.FromJSON " type " where" q)
 #+END_SRC
diff --git a/emacs-lisp/templates.lisp b/emacs-lisp/templates.lisp
index a6b3c3d..1fae6a7 100644
--- a/emacs-lisp/templates.lisp
+++ b/emacs-lisp/templates.lisp
@@ -172,3 +172,5 @@ haskell-mode
      (s fname) " " (p "pattern") " = " (p "undefined"))
 ; guarded fn
 (<- (p "x") " <- " (p "undefined"))
+(aeson "instance A.ToJSON " (p "" type) " where" n
+       "instance A.FromJSON " type " where" q)