diff --git a/csrc/trtllm_fused_moe_kernel_launcher.cu b/csrc/trtllm_fused_moe_kernel_launcher.cu
index a52f5e0dce..e8d92fb213 100644
--- a/csrc/trtllm_fused_moe_kernel_launcher.cu
+++ b/csrc/trtllm_fused_moe_kernel_launcher.cu
@@ -1986,15 +1986,16 @@ Array<Tensor> trtllm_fp4_block_scale_moe(
   int hidden_size = hidden_states.size(1);
   if (hidden_states.dtype() == dl_uint8) hidden_size *= 2;
 
-  int hidden_states_scale_vec_size = -1;
+  int64_t hidden_states_scale_vec_size = -1;
   if (hidden_states_scale.has_value()) {
-    hidden_states_scale_vec_size = (num_tokens * hidden_size) / hidden_states_scale.value().numel();
+    hidden_states_scale_vec_size =
+        (static_cast<int64_t>(num_tokens) * hidden_size) / hidden_states_scale.value().numel();
   }
   int64_t intermediate_size_factor =
       isGatedActivation(static_cast<ActivationType>(act_type)) ? 2 : 1;
-  int weight_scale_vec_size =
-      (local_num_experts * intermediate_size * intermediate_size_factor * hidden_size) /
-      gemm1_weights_scale.numel();
+  int64_t weight_scale_vec_size = (static_cast<int64_t>(local_num_experts) * intermediate_size *
+                                   intermediate_size_factor * hidden_size) /
+                                  gemm1_weights_scale.numel();
 
   TVM_FFI_ICHECK(weight_scale_vec_size == 16 || weight_scale_vec_size == 32)
       << "unsupported weight_scale_vec_size.";