diff --git a/R-package/tests/testthat/helper.R b/R-package/tests/testthat/helper.R
index 9c928c1f71d1..0777ed287405 100644
--- a/R-package/tests/testthat/helper.R
+++ b/R-package/tests/testthat/helper.R
@@ -11,6 +11,7 @@
 #   the check farm is a shared resource and will typically be running many checks simultaneously.
 #
 .LGB_MAX_THREADS <- 2L
+setLGBMthreads(.LGB_MAX_THREADS)
 
 # by default, how much should results in tests be allowed to differ from hard-coded expected numbers?
 .LGB_NUMERIC_TOLERANCE <- 1e-6
diff --git a/include/LightGBM/utils/openmp_wrapper.h b/include/LightGBM/utils/openmp_wrapper.h
index 1c77dffe1b76..b9a8ea2982fc 100644
--- a/include/LightGBM/utils/openmp_wrapper.h
+++ b/include/LightGBM/utils/openmp_wrapper.h
@@ -18,6 +18,8 @@ LIGHTGBM_EXTERN_C int LGBM_DEFAULT_NUM_THREADS;
 
 #include <LightGBM/utils/log.h>
 
+#include <omp.h>
+
 #include <exception>
 #include <memory>
 #include <mutex>
@@ -112,9 +114,9 @@ class ThreadExceptionHelper {
   /** Fall here if no OPENMP support, so just
       simulate a single thread running.
       All #pragma omp should be ignored by the compiler **/
-  inline int OMP_NUM_THREADS() __GOMP_NOTHROW { return 1; }
   inline void OMP_SET_NUM_THREADS(int) __GOMP_NOTHROW {}
   inline int omp_get_thread_num() __GOMP_NOTHROW {return 0;}
+  inline int OMP_NUM_THREADS() __GOMP_NOTHROW { return 1; }
 #ifdef __cplusplus
 }  // extern "C"
 #endif