diff --git a/embassy/src/util/forever.rs b/embassy/src/util/forever.rs
index b1bfd166..9b1f8bb3 100644
--- a/embassy/src/util/forever.rs
+++ b/embassy/src/util/forever.rs
@@ -22,7 +22,7 @@ impl<T> Forever<T> {
         if self
             .used
             .compare_exchange(false, true, Ordering::AcqRel, Ordering::Acquire)
-            .is_ok()
+            .is_err()
         {
             panic!("Forever.put() called multiple times");
         }