diff --git a/src/extensions.rs b/src/extensions.rs
index c41bbfc3..f16d762e 100644
--- a/src/extensions.rs
+++ b/src/extensions.rs
@@ -48,7 +48,7 @@ impl Extensions {
     /// Insert a type into this `Extensions`.
     ///
     /// If a extension of this type already existed, it will
-    /// be returned.
+    /// be returned and replaced with the new one.
     ///
     /// # Example
     ///