diff --git a/readme.md b/readme.md
index e2368507..c2ceda33 100644
--- a/readme.md
+++ b/readme.md
@@ -86,6 +86,10 @@ Options:
 | `struct`, `enum`, `union` | Composite types |
 | `Closure(args) -> ret` | Closure type |
 
+A `[*]T` many-pointer carries no length, so it does **not** implicitly coerce to
+a slice `[]T` — slice it with a length: `ptr[0..len]`. (A fixed array `[N]T`
+*does* coerce to `[]T` — its length is known.)
+
 **Numeric limits.** A field-like access on a builtin integer type name folds to
 a compile-time constant of that type: `i64.max` → `9223372036854775807`,
 `u8.min` → `0`, `i3.max` → `3`. It works for every width `i1`..`i64` / `u1`..`u64`