diff --git a/test/topology_custom/test_tablets.py b/test/topology_custom/test_tablets.py
index 8cb47b311b..bcb1ae9b7d 100644
--- a/test/topology_custom/test_tablets.py
+++ b/test/topology_custom/test_tablets.py
@@ -110,6 +110,8 @@ async def test_tablet_rf_change(manager: ManagerClient, direction):
     cfg = {'enable_user_defined_functions': False,
            'experimental_features': ['tablets']}
     servers = await manager.servers_add(3, config=cfg)
+    for s in servers:
+        await manager.api.disable_tablet_balancing(s.ip_addr)
 
     cql = manager.get_cql()
     res = await cql.run_async("SELECT data_center FROM system.local")
@@ -146,7 +148,7 @@ async def test_tablet_rf_change(manager: ManagerClient, direction):
     logger.info(f"Checking {rf_to} re-allocated replicas")
     await check_allocated_replica(rf_to)
 
-    fragments = { pk: [] for pk in random.sample(range(128), 17) }
+    fragments = { pk: set() for pk in random.sample(range(128), 17) }
     for s in servers:
         host_id = await manager.get_host_id(s.server_id)
         host = await wait_for_cql_and_get_hosts(cql, [s], time.time() + 30)
@@ -155,7 +157,7 @@ async def test_tablet_rf_change(manager: ManagerClient, direction):
             res = await cql.run_async(f"SELECT partition_region FROM MUTATION_FRAGMENTS(test.test) WHERE pk={k}", host=host[0])
             for fragment in res:
                 if fragment.partition_region == 0: # partition start
-                    fragments[k].append(host_id)
+                    fragments[k].add(host_id)
     logger.info("Checking fragments")
     for k in fragments:
         assert len(fragments[k]) == rf_to, f"Found mutations for {k} key on {fragments[k]} hosts, but expected only {rf_to} of them"