diff --git a/src/route.rs b/src/route.rs
index 4ff3279e..1322d108 100644
--- a/src/route.rs
+++ b/src/route.rs
@@ -169,6 +169,8 @@ impl<S: 'static> Route<S> {
     }
 
     /// Set async handler function, use request extractor for parameters.
+    /// Also this method needs to be used if your handler function returns
+    /// `impl Future<>`
     ///
     /// ```rust
     /// # extern crate bytes;