diff --git a/python/sglang/srt/layers/attention/qsa/qsa_indexer.py b/python/sglang/srt/layers/attention/qsa/qsa_indexer.py
index 4de4c6a8d..a15585835 100644
--- a/python/sglang/srt/layers/attention/qsa/qsa_indexer.py
+++ b/python/sglang/srt/layers/attention/qsa/qsa_indexer.py
@@ -321,6 +321,7 @@ class QSAIndexer(MultiPlatformOp):
                 self.compress_ratio, device=member_rows.device, dtype=torch.long
             )
             source_keys = token_k
+            group_locs = group_locs.clamp_max(source_keys.shape[0] - 1)
             source_rope = metadata.extend_rope_matrix
             if source_rope is None:
                 source_rope = build_rope_position_matrix(