diff --git a/src/mailbox.rs b/src/mailbox.rs
index b11025dbf24105af04fd3a5423d52ce6d09d6f9d..1603220fed715345d7723f83b4dfd375b75d1a4f 100644
--- a/src/mailbox.rs
+++ b/src/mailbox.rs
@@ -56,8 +56,10 @@ use std::time::Duration;
 /// assert!(mailbox.try_receive_all().is_empty());
 /// ```
 
+#[derive(Default)]
 pub struct Mailbox<T>(Rc<Inner<T>>);
 
+#[derive(Default)]
 struct Inner<T> {
     cond: Rc<fiber::Cond>,
     content: RefCell<Vec<T>>,