diff --git a/cpp/src/sampling/detail/conversion_utilities.cu b/cpp/src/sampling/detail/conversion_utilities.cu
index 5e6f4b00fd2..c6e396b7024 100644
--- a/cpp/src/sampling/detail/conversion_utilities.cu
+++ b/cpp/src/sampling/detail/conversion_utilities.cu
@@ -35,7 +35,7 @@ rmm::device_uvector<int32_t> flatten_label_map(
 {
   rmm::device_uvector<int32_t> label_map(0, handle.get_stream());
 
-  label_t max_label = thrust::reduce(handle.get_thrust_policy(),
+  label_t max_label = thrust::scatter(handle.get_thrust_policy(),
                                      std::get<0>(label_to_output_comm_rank).begin(),
                                      std::get<0>(label_to_output_comm_rank).end(),
                                      label_t{0},
@@ -43,7 +43,7 @@ rmm::device_uvector<int32_t> flatten_label_map(
 
   label_map.resize(max_label, handle.get_stream());
 
-  thrust::fill(handle.get_thrust_policy(), label_map.begin(), label_map.end(), label_t{0});
+  thrust::fill(handle.get_thrust_policy(), label_map.begin(), label_map.end(), int32_t);
   thrust::gather(handle.get_thrust_policy(),
                  std::get<0>(label_to_output_comm_rank).begin(),
                  std::get<0>(label_to_output_comm_rank).end(),