diff --git a/src/kernel/thread_manager.rs b/src/kernel/thread_manager.rs
index 6878c63..870a9fc 100644
--- a/src/kernel/thread_manager.rs
+++ b/src/kernel/thread_manager.rs
@@ -79,6 +79,7 @@ impl ThreadManager {
                     self.debug(format!("switching from \"{}\" to \"{}\"", old2.borrow().get_name(), next_thread.borrow().get_name()));
                     self.thread_restore_processor_state(machine, Rc::clone(&next_thread));
                     // next_thread.restore_simulator_state();
+                    debug_assert!(!self.ready_list.contains(&next_thread));
                     self.set_g_current_thread(Some(next_thread));
                 }
             },
@@ -111,6 +112,7 @@ impl ThreadManager {
     pub fn thread_join(&mut self, machine: &mut Machine, waiter: Rc<RefCell<Thread>>, waiting_for: Rc<RefCell<Thread>>) {
         let waiting_for = Rc::clone(&waiting_for);
         while self.get_g_alive().contains(&waiting_for) {
+            self.debug(format!("Joining \"{}\" to \"{}\"", waiter.borrow().get_name(), waiting_for.borrow().get_name()));
             self.thread_yield(machine, Rc::clone(&waiter));
         }
     }