diff --git a/app/Gyehoek/ANF/Syntax.hs b/app/Gyehoek/ANF/Syntax.hs
index 2b6a820..5bc3a34 100644
--- a/app/Gyehoek/ANF/Syntax.hs
+++ b/app/Gyehoek/ANF/Syntax.hs
@@ -333,7 +333,7 @@ sizeofScm :: Integral a => a
 sizeofScm = 8
 
 lowerCons
-  :: (GenSym :> es)
+  :: (GenSym :> es, Writer (Vector QBE.DataDef) :> es)
   => Name -> QBE.Val -> QBE.Val -> Exp
   -> (QBE.Val -> Eff es BlockBuilder)
   -> Eff es BlockBuilder