diff --git a/library/alloc/tests/vec.rs b/library/alloc/tests/vec.rs
index 53b0d0a2718..5f7a9399453 100644
--- a/library/alloc/tests/vec.rs
+++ b/library/alloc/tests/vec.rs
@@ -1511,6 +1511,9 @@ fn test_stable_pointers() {
     // Test that, if we reserved enough space, adding and removing elements does not
     // invalidate references into the vector (such as `v0`).  This test also
     // runs in Miri, which would detect such problems.
+    // Note that this test does *not* constitute a stable guarantee that all these functions do not
+    // reallocate! Only what is explicitly documented at
+    // <https://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#guarantees> is stably guaranteed.
     let mut v = Vec::with_capacity(128);
     v.push(13);