diff --git a/preserves-schema.md b/preserves-schema.md
index 9194f48..f32a696 100644
--- a/preserves-schema.md
+++ b/preserves-schema.md
@@ -182,16 +182,15 @@ Intersections are an experimental feature. They can be used to express
 *optional dictionary entries*:[^not-ideal-optional-encoding]
 
     MyDict = {a: int, b: string} & @c MaybeC .
-    MaybeC = @present {c: symbol} / @absent {} .
+    MaybeC = @present {c: symbol} / @invalid {c: any} / @absent {} .
 
 It is not yet clear whether they pull their weight. In particular, the
 semantics of serializing a value defined by intersection are not
 completely clear.
 
-[^not-ideal-optional-encoding]: This encoding is not ideal. Given a
-    term `{a: 1, b: "", c: sym}`, it will yield a `present` result,
-    and given `{a: 1, b: ""}`, will yield an `absent` result; but
-    `absent` will also result from `{a: 1, b: "", c: "notasymbol"}`.
+[^not-ideal-optional-encoding]: This encoding is not ideal. It passes
+    responsibility for checking for invalid inputs up to the user,
+    rather than handling it completely at the Schema layer.
 
 ### Patterns.