diff --git a/src/liballoc/collections/linked_list.rs b/src/liballoc/collections/linked_list.rs
index 2ef84dbade0fb..ba46fafaf169f 100644
--- a/src/liballoc/collections/linked_list.rs
+++ b/src/liballoc/collections/linked_list.rs
@@ -627,7 +627,9 @@ impl<T> LinkedList<T> {
         self.pop_front_node().map(Node::into_element)
     }
 
-    /// Appends an element to the back of a list
+    /// Appends an element to the back of a list.
+    ///
+    /// This operation should compute in O(1) time.
     ///
     /// # Examples
     ///
@@ -647,6 +649,8 @@ impl<T> LinkedList<T> {
     /// Removes the last element from a list and returns it, or `None` if
     /// it is empty.
     ///
+    /// This operation should compute in O(1) time.
+    ///
     /// # Examples
     ///
     /// ```