diff --git a/spec.md b/spec.md
index 4212dfe..1231a24 100644
--- a/spec.md
+++ b/spec.md
@@ -1363,7 +1363,8 @@ An application may pre-declare additional names
 to provide domain-specific functions to that file, for example.
 These additional functions may have side effects on the application.
 Starlark programs cannot change the set of predeclared bindings
-or assign new values to them.
+or assign new values to them (but they can be redefined in a
+smaller block).
 
 Nested beneath the predeclared block is the _module_ block,
 which contains the bindings of the current module.