diff --git a/realhf/system/master_worker.py b/realhf/system/master_worker.py
index 45411219..c7a5aa16 100755
--- a/realhf/system/master_worker.py
+++ b/realhf/system/master_worker.py
@@ -551,7 +551,7 @@ async def model_rpc_request_func(
             assert sample.bs % dp_size == 0
             min_n_seqs_per_dp = sample.bs // dp_size
         else:
-            min_n_seqs_per_dp = 1
+            min_n_seqs_per_dp = rpc.n_mbs
         split_spec = sample.get_split_spec(dp_size, min_size=min_n_seqs_per_dp)
         partitions = split_spec.partitions
         target_mapping = {i: list(range(v[0], v[1])) for i, v in enumerate(partitions)}