diff --git a/include/LightGBM/bin.h b/include/LightGBM/bin.h
index ffb8f2844..de1bb6eb9 100644
--- a/include/LightGBM/bin.h
+++ b/include/LightGBM/bin.h
@@ -63,8 +63,7 @@ inline static void Int32HistogramSumReducer(const char* src, char* dst, int type
   const int64_t* src_ptr = reinterpret_cast<const int64_t*>(src);
   int64_t* dst_ptr = reinterpret_cast<int64_t*>(dst);
   const comm_size_t steps = (len + (type_size * 2) - 1) / (type_size * 2);
-  const int num_threads = OMP_NUM_THREADS();
-  #pragma omp parallel for schedule(static) num_threads(num_threads)
+  #pragma omp parallel for schedule(static) num_threads(OMP_NUM_THREADS())
   for (comm_size_t i = 0; i < steps; ++i) {
     dst_ptr[i] += src_ptr[i];
   }
@@ -74,8 +73,7 @@ inline static void Int16HistogramSumReducer(const char* src, char* dst, int type
   const int32_t* src_ptr = reinterpret_cast<const int32_t*>(src);
   int32_t* dst_ptr = reinterpret_cast<int32_t*>(dst);
   const comm_size_t steps = (len + (type_size * 2) - 1) / (type_size * 2);
-  const int num_threads = OMP_NUM_THREADS();
-  #pragma omp parallel for schedule(static) num_threads(num_threads)
+  #pragma omp parallel for schedule(static) num_threads(OMP_NUM_THREADS())
   for (comm_size_t i = 0; i < steps; ++i) {
     dst_ptr[i] += src_ptr[i];
   }