diff --git a/vllm/v1/worker/gpu_model_runner.py b/vllm/v1/worker/gpu_model_runner.py
index eebdbcc621c69..ee339e22cea90 100644
--- a/vllm/v1/worker/gpu_model_runner.py
+++ b/vllm/v1/worker/gpu_model_runner.py
@@ -2807,7 +2807,7 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
 
         dummy_decoder_data = self.mm_registry.get_decoder_dummy_data(
             model_config=self.model_config,
-            seq_len=self.max_num_tokens,
+            seq_len=self.max_model_len,
             mm_counts={modality: 1},
             cache=self.mm_budget.cache,
         )
diff --git a/vllm/v1/worker/tpu_model_runner.py b/vllm/v1/worker/tpu_model_runner.py
index 4cbf991a14c11..4a2adb1e6510d 100644
--- a/vllm/v1/worker/tpu_model_runner.py
+++ b/vllm/v1/worker/tpu_model_runner.py
@@ -1795,7 +1795,7 @@ class TPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
 
         dummy_decoder_data = self.mm_registry.get_decoder_dummy_data(
             model_config=self.model_config,
-            seq_len=self.max_num_tokens,
+            seq_len=self.max_model_len,
             mm_counts={modality: 1},
             cache=self.mm_budget.cache,
         )