diff --git a/src/libcollections/btree/map.rs b/src/libcollections/btree/map.rs
index 39925ddff84..178d7a4a052 100644
--- a/src/libcollections/btree/map.rs
+++ b/src/libcollections/btree/map.rs
@@ -319,8 +319,9 @@ impl<K: Ord, V> BTreeMap<K, V> {
     ///
     /// If the map did not have this key present, `None` is returned.
     ///
-    /// If the map did have this key present, that value is returned, and the
-    /// entry is not updated. See the [module-level documentation] for more.
+    /// If the map did have this key present, the key is not updated, the
+    /// value is updated and the old value is returned.
+    /// See the [module-level documentation] for more.
     ///
     /// [module-level documentation]: index.html#insert-and-complex-keys
     ///
diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
index 965226f6355..b8482b3a2dc 100644
--- a/src/libstd/collections/hash/map.rs
+++ b/src/libstd/collections/hash/map.rs
@@ -1108,8 +1108,9 @@ impl<K, V, S> HashMap<K, V, S>
     ///
     /// If the map did not have this key present, `None` is returned.
     ///
-    /// If the map did have this key present, that value is returned, and the
-    /// entry is not updated. See the [module-level documentation] for more.
+    /// If the map did have this key present, the key is not updated, the
+    /// value is updated and the old value is returned.
+    /// See the [module-level documentation] for more.
     ///
     /// [module-level documentation]: index.html#insert-and-complex-keys
     ///