diff --git a/FFTXlib/src/fft_parallel.f90 b/FFTXlib/src/fft_parallel.f90
index 28ba8f3ff..13cd87275 100644
--- a/FFTXlib/src/fft_parallel.f90
+++ b/FFTXlib/src/fft_parallel.f90
@@ -196,7 +196,9 @@ SUBROUTINE many_cft3s( f, dfft, isgn, howmany )
   USE fft_scatter, ONLY : fft_scatter_xy, fft_scatter_yz, &
          fft_scatter_tg_opt, fft_scatter_many_xy, fft_scatter_many_yz
   USE fft_types,   ONLY : fft_type_descriptor
+#if defined(_OPENMP)
   USE omp_lib
+#endif
   !
   IMPLICIT NONE
   !
diff --git a/FFTXlib/src/fft_types.f90 b/FFTXlib/src/fft_types.f90
index 350743b8e..3118f386a 100644
--- a/FFTXlib/src/fft_types.f90
+++ b/FFTXlib/src/fft_types.f90
@@ -22,7 +22,9 @@ MODULE fft_types
 #endif
   USE fft_support, ONLY : good_fft_order, good_fft_dimension
   USE fft_param
+#if defined(_OPENMP)
   USE omp_lib
+#endif
   IMPLICIT NONE
   PRIVATE
   SAVE