assert before we set the suppressed

core/src/main/java/org/elasticsearch/index/translog/Translog.java

@@ -580,8 +580,8 @@ public class Translog extends AbstractIndexShardComponent implements IndexShardC
                 // don't do anything in this case. The AlreadyClosedException comes from TranslogWriter and we should not add it as suppressed because
                 // will contain the Exception ex as cause. See also https://github.com/elastic/elasticsearch/issues/15941
             } catch (Exception inner) {
-                ex.addSuppressed(inner);
                 assert (ex != inner.getCause());
+                ex.addSuppressed(inner);
             }
         }
     }