diff --git a/test_runner/batch_others/test_wal_acceptor.py b/test_runner/batch_others/test_wal_acceptor.py
index bdc526a125..8f87ff041f 100644
--- a/test_runner/batch_others/test_wal_acceptor.py
+++ b/test_runner/batch_others/test_wal_acceptor.py
@@ -108,14 +108,14 @@ def test_many_timelines(zenith_env_builder: ZenithEnvBuilder):
 
             for flush_lsn, commit_lsn in zip(m.flush_lsns, m.commit_lsns):
                 # Invariant. May be < when transaction is in progress.
-                assert commit_lsn <= flush_lsn
+                assert commit_lsn <= flush_lsn, f"timeline_id={timeline_id}, timeline_detail={timeline_detail}, sk_metrics={sk_metrics}"
             # We only call collect_metrics() after a transaction is confirmed by
             # the compute node, which only happens after a consensus of safekeepers
             # has confirmed the transaction. We assume majority consensus here.
             assert (2 * sum(m.last_record_lsn <= lsn
-                            for lsn in m.flush_lsns) > zenith_env_builder.num_safekeepers)
+                            for lsn in m.flush_lsns) > zenith_env_builder.num_safekeepers), f"timeline_id={timeline_id}, timeline_detail={timeline_detail}, sk_metrics={sk_metrics}"
             assert (2 * sum(m.last_record_lsn <= lsn
-                            for lsn in m.commit_lsns) > zenith_env_builder.num_safekeepers)
+                            for lsn in m.commit_lsns) > zenith_env_builder.num_safekeepers), f"timeline_id={timeline_id}, timeline_detail={timeline_detail}, sk_metrics={sk_metrics}"
             timeline_metrics.append(m)
         log.info(f"{message}: {timeline_metrics}")
         return timeline_metrics