diff --git a/Missing.md b/Missing.md
index bf6f6f1ae505b4d3163b13ff35e8472269ccbb18..b43c0db5f7bbd604f1eb0c31543f377c5f56770c 100644
--- a/Missing.md
+++ b/Missing.md
@@ -5,3 +5,7 @@ Missing APIs from the types we cover (APIs have been added after this formalizat
 * Structural conversion for slices.  The matching operations in our model would be
   `&mut Cell<(A, B)>` -> `&mut (Cell<A>, Cell<B>)` and
   `&Cell<(A, B)>` -> `&(Cell<A>, Cell<B>)` (both being NOPs).
+
+# ZST
+
+* Something like the example from <https://github.com/rust-lang/unsafe-code-guidelines/issues/168#issuecomment-512528361>