diff --git a/vllm/model_executor/models/mamba.py b/vllm/model_executor/models/mamba.py
index ca8d58fd3d6aa..a76c3757be739 100644
--- a/vllm/model_executor/models/mamba.py
+++ b/vllm/model_executor/models/mamba.py
@@ -538,20 +538,20 @@ def _prepare_current_run_mamba_cache(
 
     def copy_inputs_before_cuda_graphs(self, input_buffers, **kwargs):
         """
-        Copy the relevant Mamba cache into the CUDA graph input buffer
-        that was provided during the capture runs
-        (MambaForCausalLM.mamba_gc_cache_buffer).
+        Copy the relevant Mamba cache into the CUDA graph input buffer 
+        that was provided during the capture runs 
+        (MambaForCausalLM.mamba_gc_cache_buffer). 
         """
         assert all(
             key in kwargs
             for key in ["request_ids_to_seq_ids", "finished_requests_ids"])
         request_ids_to_seq_ids = kwargs["request_ids_to_seq_ids"]
-        batch_size = len(request_ids_to_seq_ids)
+        cg_batch_size = input_buffers['input_ids'].shape[0]
         (
             current_mamba_cache,
             indices,
         ) = self._prepare_current_run_mamba_cache(request_ids_to_seq_ids,
-                                                  batch_size)
+                                                  cg_batch_size)
         self.current_indices = indices
         finished_requests_ids = kwargs["finished_requests_ids"]
         self._release_mamba_cache(finished_requests_ids)