diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index af76fddaced7c..8d79de80695e9 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -3501,7 +3501,13 @@ impl<T: ?Sized, A: Allocator> Weak<T, A> {
     /// Attempts to upgrade the `Weak` pointer to an [`Rc`], delaying
     /// dropping of the inner value if successful.
     ///
-    /// Returns [`None`] if the inner value has since been dropped.
+    /// Returns [`None`] in the following cases:
+    ///
+    /// 1. The inner value has since been dropped or moved out.
+    ///
+    /// 2. This `Weak` does not point to an allocation.
+    ///
+    /// 3. The owning reference this `Weak` is associated with is either not fully-constructed or does not allow an upgrade.
     ///
     /// # Examples
     ///
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index af1eaf2015e9d..fe54cf62f6111 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -3232,7 +3232,13 @@ impl<T: ?Sized, A: Allocator> Weak<T, A> {
     /// Attempts to upgrade the `Weak` pointer to an [`Arc`], delaying
     /// dropping of the inner value if successful.
     ///
-    /// Returns [`None`] if the inner value has since been dropped.
+    /// Returns [`None`] in the following cases:
+    ///
+    /// 1. The inner value has since been dropped or moved out.
+    ///
+    /// 2. This `Weak` does not point to an allocation.
+    ///
+    /// 3. The owning reference this `Weak` is associated with is either not fully-constructed or does not allow an upgrade.
     ///
     /// # Examples
     ///