diff --git a/src/Fortran_libraries/SERIAL_src/IO/write_pick_sph_spectr_data.F90 b/src/Fortran_libraries/SERIAL_src/IO/write_pick_sph_spectr_data.F90
index 9a601033..0be4716a 100644
--- a/src/Fortran_libraries/SERIAL_src/IO/write_pick_sph_spectr_data.F90
+++ b/src/Fortran_libraries/SERIAL_src/IO/write_pick_sph_spectr_data.F90
@@ -35,7 +35,10 @@ module write_pick_sph_spectr_data
 !
       implicit  none
 !
+#ifdef ZLIB_IO
       private :: gz_write_picked_spec_data
+#endif
+!
       private :: dup_pick_sph_file_header_base
 !
 ! -----------------------------------------------------------------------
diff --git a/src/Fortran_libraries/SERIAL_src/IO_ZLIB/gz_layer_spectr_monitor_IO.F90 b/src/Fortran_libraries/SERIAL_src/IO_ZLIB/gz_layer_spectr_monitor_IO.F90
index 32ac0031..e0ca41d2 100644
--- a/src/Fortran_libraries/SERIAL_src/IO_ZLIB/gz_layer_spectr_monitor_IO.F90
+++ b/src/Fortran_libraries/SERIAL_src/IO_ZLIB/gz_layer_spectr_monitor_IO.F90
@@ -55,7 +55,9 @@ module gz_layer_spectr_monitor_IO
 !
       implicit none
 !
+#ifdef ZLIB_IO
       private :: gz_write_layer_spectr_monitor
+#endif
 !
 ! -----------------------------------------------------------------------
 !
diff --git a/src/Fortran_libraries/SERIAL_src/IO_ZLIB/gz_volume_spectr_monitor_IO.F90 b/src/Fortran_libraries/SERIAL_src/IO_ZLIB/gz_volume_spectr_monitor_IO.F90
index 78911806..ad4aa67a 100644
--- a/src/Fortran_libraries/SERIAL_src/IO_ZLIB/gz_volume_spectr_monitor_IO.F90
+++ b/src/Fortran_libraries/SERIAL_src/IO_ZLIB/gz_volume_spectr_monitor_IO.F90
@@ -46,7 +46,9 @@ module gz_volume_spectr_monitor_IO
 !
       implicit none
 !
+#ifdef ZLIB_IO
       private :: gz_write_volume_spectr_monitor
+#endif
 !
 ! -----------------------------------------------------------------------
 !