diff --git a/crates/futures/src/lib.rs b/crates/futures/src/lib.rs
index 3711a666..ca35b0ab 100644
--- a/crates/futures/src/lib.rs
+++ b/crates/futures/src/lib.rs
@@ -378,7 +378,14 @@ fn _future_to_promise(future: Box<Future<Item = JsValue, Error = JsValue>>) -> P
     }
 }
 
-/// Spawns a future.
+/// Converts a Rust `Future` on a local task queue.
+///
+/// The `future` provided must adhere to `'static` because it'll be scheduled
+/// to run in the background and cannot contain any stack references.
+///
+/// # Panics
+///
+/// This function has the same panic behavior as `future_to_promise`.
 pub fn spawn_local<F>(future: F)
 where
     F: Future<Item = (), Error = ()> + 'static,