diff --git a/test/distributed/org/apache/cassandra/distributed/impl/Instance.java b/test/distributed/org/apache/cassandra/distributed/impl/Instance.java
index ab5df4a610..a6d838e3fe 100644
--- a/test/distributed/org/apache/cassandra/distributed/impl/Instance.java
+++ b/test/distributed/org/apache/cassandra/distributed/impl/Instance.java
@@ -810,7 +810,9 @@ public class Instance extends IsolatedExecutor implements IInvokableInstance
     @Override
     public void postStartup()
     {
-        StorageService.instance.doAuthSetup(false);
+        sync(() ->
+            StorageService.instance.doAuthSetup(false)
+        ).run();
     }
 
     private void mkdirs()