diff --git a/compiler/stgSyn/CoreToStg.lhs b/compiler/stgSyn/CoreToStg.lhs
index 80b81a68e4d6b7f2130413bb144e0398e2db6e84..9c5bc10293571d8b743ee6b77d9e1212d671fe67 100644
--- a/compiler/stgSyn/CoreToStg.lhs
+++ b/compiler/stgSyn/CoreToStg.lhs
@@ -144,7 +144,8 @@ import Control.Monad (liftM, ap)
 -- to the code for `x'.
 --
 -- All of this is provided x is:
---   1. non-updatable;
+--   1. non-updatable - it must have at least one parameter (see Note
+--      [Join point abstraction]);
 --   2. guaranteed to be entered before the stack retreats -- ie x is not
 --      buried in a heap-allocated closure, or passed as an argument to
 --      something;