diff --git a/cpp/src/reductions/scan.cu b/cpp/src/reductions/scan.cu
index 011b34031fe..6c42c8aa3f7 100644
--- a/cpp/src/reductions/scan.cu
+++ b/cpp/src/reductions/scan.cu
@@ -116,8 +116,9 @@ struct scan_dispatcher {
       thrust::find_if_not(
         rmm::exec_policy(stream), v, v + input_view.size(), thrust::identity<bool>{}) -
       v;
-    cudf::set_null_mask(
-      static_cast<cudf::bitmask_type*>(mask.data()), 0, first_null_position, true);
+    if (first_null_position > 0)
+      cudf::set_null_mask(
+        static_cast<cudf::bitmask_type*>(mask.data()), 0, first_null_position, true);
     cudf::set_null_mask(
       static_cast<cudf::bitmask_type*>(mask.data()), first_null_position, input_view.size(), false);
     return mask;