diff --git a/mmcv/ops/csrc/parrots/iou3d.cpp b/mmcv/ops/csrc/parrots/iou3d.cpp
index 4d785703e..8af4f05da 100644
--- a/mmcv/ops/csrc/parrots/iou3d.cpp
+++ b/mmcv/ops/csrc/parrots/iou3d.cpp
@@ -75,6 +75,7 @@ void iou3d_nms_forward(Tensor boxes, Tensor keep, Tensor keep_num,
 
   const int col_blocks =
       (boxes_num + THREADS_PER_BLOCK_NMS - 1) / THREADS_PER_BLOCK_NMS;
+
   Tensor mask =
       at::empty({boxes_num, col_blocks}, boxes.options().dtype(at::kLong));
   unsigned long long *mask_data =
@@ -117,7 +118,8 @@ void iou3d_nms_normal_forward(Tensor boxes, Tensor keep, Tensor keep_num,
   int64_t *keep_data = keep.data_ptr<int64_t>();
   int64_t *keep_num_data = keep_num.data_ptr<int64_t>();
 
-  const int col_blocks = DIVUP(boxes_num, THREADS_PER_BLOCK_NMS);
+  const int col_blocks =
+      (boxes_num + THREADS_PER_BLOCK_NMS - 1) / THREADS_PER_BLOCK_NMS;
 
   Tensor mask =
       at::empty({boxes_num, col_blocks}, boxes.options().dtype(at::kLong));