diff --git a/r9/src/xtimer.rs b/r9/src/xtimer.rs
index 6786fdb..9f21cb6 100644
--- a/r9/src/xtimer.rs
+++ b/r9/src/xtimer.rs
@@ -261,7 +261,10 @@ impl XTimer {
     pub fn update(this: &Rc::<RefCell::<XTimer>>) {
         let tick = (*this.borrow().get_tick_count.as_ref().unwrap())();
         let work_list = this.borrow().work_list.clone();
-        while this.borrow_mut().fetch_work_list(tick) {
+        loop {
+            if !this.borrow_mut().fetch_work_list(tick) {
+                break;
+            }
             while !work_list.borrow().empty() {
                 {
                     let timer = &work_list.borrow().first_entry();