diff --git a/src/util/util_atomic.ml b/src/util/util_atomic.ml
index 7fbbc0fa..45dfef5c 100644
--- a/src/util/util_atomic.ml
+++ b/src/util/util_atomic.ml
@@ -13,5 +13,6 @@ let update_cas (type res) (self : 'a Atomic.t) (f : 'a -> res * 'a) : res =
 
       Opentelemetry_domain.relax_loop !backoff;
       backoff := min 128 (2 * !backoff)
-    done
+    done;
+    assert false
   with Ret r -> r