diff --git a/guide/src/reference/types/boxed-number-slices.md b/guide/src/reference/types/boxed-number-slices.md
index 2d65efd37cc..4196d48ee06 100644
--- a/guide/src/reference/types/boxed-number-slices.md
+++ b/guide/src/reference/types/boxed-number-slices.md
@@ -8,6 +8,10 @@
 from the Wasm linear memory when returning a boxed slice to JavaScript, and vice
 versa when receiving a JavaScript `TypedArray` as a boxed slice in Rust.
 
+> **Note:** Numeric `MaybeUninit<T>` can always be assumed to be initialized
+> upon transmission from Rust to JS and vice-versa. However, uninitialized
+> values coming from Rust might contain unspecified values.
+
 ## Example Rust Usage
 
 ```rust
diff --git a/guide/src/reference/types/number-slices.md b/guide/src/reference/types/number-slices.md
index 0fedc3d3faa..11da99673f9 100644
--- a/guide/src/reference/types/number-slices.md
+++ b/guide/src/reference/types/number-slices.md
@@ -4,6 +4,10 @@
 |:---:|:---:|:---:|:---:|:---:|:---:|:---:|
 | No | Yes | Yes | No | No | No | A JavaScript `TypedArray` view of the Wasm memory for the boxed slice of the appropriate type (`Int32Array`, `Uint8Array`, etc) |
 
+> **Note:** Numeric `MaybeUninit<T>` can always be assumed to be initialized
+> upon transmission from Rust to JS and vice-versa. However, uninitialized
+> values coming from Rust might contain unspecified values.
+
 ## Example Rust Usage
 
 ```rust