diff --git a/deepinfer/model_executor/models/v4_modules/index_attn.py b/deepinfer/model_executor/models/v4_modules/index_attn.py
index 345b12c..9d4f955 100644
--- a/deepinfer/model_executor/models/v4_modules/index_attn.py
+++ b/deepinfer/model_executor/models/v4_modules/index_attn.py
@@ -98,6 +98,15 @@ class MQA(nn.Module):
         candidate_cfg = shared_topology.candidate_source_cfg[candidate_source] if candidate_source is not None else None
         self.is_candidate_topk_source = shared_topology is not None and shared_topology.is_candidate_source_layer(self.layer_idx)
         self.use_candidate_topk = candidate_source is not None and not self.is_candidate_topk_source
+        if (
+            PLATFORM.is_neuron
+            and self.is_candidate_topk_source
+            and candidate_cfg is not None
+            and cfg.runtime_max_model_len <= candidate_cfg.candidate_topk_blocks * candidate_cfg.candidate_block_size
+        ):
+            # Neuron: every consumer skips the vacuous filter (below), so nothing reads the candidate blocks; and with
+            # fewer blocks than candidate_topk_blocks the block top-k would not be defined.
+            self.is_candidate_topk_source = False
         if (
             PLATFORM.is_neuron
             and self.use_candidate_topk