diff --git a/topi/python/topi/cuda/nms.py b/topi/python/topi/cuda/nms.py
index 3cdc02e58aec..e0d71559f1a0 100644
--- a/topi/python/topi/cuda/nms.py
+++ b/topi/python/topi/cuda/nms.py
@@ -35,7 +35,7 @@ def sort_ir(data, index, output):
     p_index = ib.buffer_ptr(index)
     p_out = ib.buffer_ptr(output)
     nthread_tx = max_threads
-    nthread_bx = (num_anchors + 1) // 2 // max_threads + 1
+    nthread_bx = num_anchors // max_threads + 1
     tx = tvm.thread_axis("threadIdx.x")
     bx = tvm.thread_axis("vthread")
     ib.scope_attr(tx, "thread_extent", nthread_tx)
@@ -46,10 +46,8 @@ def sort_ir(data, index, output):
 
     with ib.for_range(0, batch, for_type="unroll") as b:
         start = b * num_anchors
-        for i in range(2):
-            bbox_id = tid * 2 + i
-            with ib.if_scope(bbox_id < num_anchors):
-                p_out[start + bbox_id] = bbox_id
+        with ib.if_scope(tid < num_anchors):
+            p_out[start + tid] = tid
         # OddEvenTransposeSort
         with ib.for_range(0, p_index[b]) as k:
             with ib.if_scope(tid < (p_index[b] + 1) // 2):