diff --git a/extmod/modussl_axtls.c b/extmod/modussl_axtls.c
index 2ea1757287..aae1c86dcb 100644
--- a/extmod/modussl_axtls.c
+++ b/extmod/modussl_axtls.c
@@ -246,10 +246,10 @@ STATIC const mp_obj_type_t ussl_socket_type = {
 STATIC mp_obj_t mod_ssl_wrap_socket(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     // TODO: Implement more args
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_key, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-        { MP_QSTR_cert, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_key, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_cert, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_server_side, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
-        { MP_QSTR_server_hostname, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_server_hostname, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_do_handshake, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = true} },
     };
 
diff --git a/extmod/modussl_mbedtls.c b/extmod/modussl_mbedtls.c
index a71adc5b36..5c41ea2d84 100644
--- a/extmod/modussl_mbedtls.c
+++ b/extmod/modussl_mbedtls.c
@@ -346,10 +346,10 @@ STATIC const mp_obj_type_t ussl_socket_type = {
 STATIC mp_obj_t mod_ssl_wrap_socket(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     // TODO: Implement more args
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_key, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-        { MP_QSTR_cert, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_key, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_cert, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_server_side, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
-        { MP_QSTR_server_hostname, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_server_hostname, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_do_handshake, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = true} },
     };
 
diff --git a/extmod/network_cyw43.c b/extmod/network_cyw43.c
index 45bb6163e7..ad46714a3e 100644
--- a/extmod/network_cyw43.c
+++ b/extmod/network_cyw43.c
@@ -166,8 +166,8 @@ STATIC mp_obj_t network_cyw43_scan(size_t n_args, const mp_obj_t *pos_args, mp_m
     enum { ARG_passive, ARG_essid, ARG_bssid };
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_passive, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
-        { MP_QSTR_essid, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-        { MP_QSTR_bssid, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_essid, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_bssid, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
     };
 
     network_cyw43_obj_t *self = MP_OBJ_TO_PTR(pos_args[0]);
@@ -212,10 +212,10 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_KW(network_cyw43_scan_obj, 1, network_cyw43_scan)
 STATIC mp_obj_t network_cyw43_connect(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum { ARG_essid, ARG_key, ARG_auth, ARG_bssid, ARG_channel };
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_essid, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-        { MP_QSTR_key, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_essid, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_key, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_auth, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
-        { MP_QSTR_bssid, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_bssid, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_channel, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
     };
 
diff --git a/extmod/vfs.c b/extmod/vfs.c
index 5f5fc633d8..e459287d4b 100644
--- a/extmod/vfs.c
+++ b/extmod/vfs.c
@@ -297,10 +297,10 @@ MP_DEFINE_CONST_FUN_OBJ_1(mp_vfs_umount_obj, mp_vfs_umount);
 mp_obj_t mp_vfs_open(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum { ARG_file, ARG_mode, ARG_encoding };
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_mode, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_QSTR(MP_QSTR_r)} },
         { MP_QSTR_buffering, MP_ARG_INT, {.u_int = -1} },
-        { MP_QSTR_encoding, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_encoding, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
     };
 
     // parse args
diff --git a/extmod/vfs_fat_file.c b/extmod/vfs_fat_file.c
index fb1e582f27..5867c202cd 100644
--- a/extmod/vfs_fat_file.c
+++ b/extmod/vfs_fat_file.c
@@ -154,9 +154,9 @@ STATIC mp_uint_t file_obj_ioctl(mp_obj_t o_in, mp_uint_t request, uintptr_t arg,
 // Note: encoding is ignored for now; it's also not a valid kwarg for CPython's FileIO,
 // but by adding it here we can use one single mp_arg_t array for open() and FileIO's constructor
 STATIC const mp_arg_t file_open_args[] = {
-    { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+    { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_NONE} },
     { MP_QSTR_mode, MP_ARG_OBJ, {.u_obj = MP_OBJ_NEW_QSTR(MP_QSTR_r)} },
-    { MP_QSTR_encoding, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+    { MP_QSTR_encoding, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_rom_obj = MP_ROM_NONE} },
 };
 #define FILE_OPEN_NUM_ARGS MP_ARRAY_SIZE(file_open_args)
 
diff --git a/extmod/vfs_posix_file.c b/extmod/vfs_posix_file.c
index 30fde818eb..87c202e3b0 100644
--- a/extmod/vfs_posix_file.c
+++ b/extmod/vfs_posix_file.c
@@ -110,7 +110,7 @@ mp_obj_t mp_vfs_posix_file_open(const mp_obj_type_t *type, mp_obj_t file_in, mp_
 
 STATIC mp_obj_t vfs_posix_file_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_mode, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_QSTR(MP_QSTR_r)} },
     };
 
diff --git a/lib/utils/mpirq.c b/lib/utils/mpirq.c
index d54c15482f..1bfce649d7 100644
--- a/lib/utils/mpirq.c
+++ b/lib/utils/mpirq.c
@@ -36,7 +36,7 @@
  ******************************************************************************/
 
 const mp_arg_t mp_irq_init_args[] = {
-    { MP_QSTR_handler, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+    { MP_QSTR_handler, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
     { MP_QSTR_trigger, MP_ARG_INT, {.u_int = 0} },
     { MP_QSTR_hard, MP_ARG_BOOL, {.u_bool = false} },
 };
diff --git a/ports/esp32/esp32_partition.c b/ports/esp32/esp32_partition.c
index e5bd31af0e..50c2173cc7 100644
--- a/ports/esp32/esp32_partition.c
+++ b/ports/esp32/esp32_partition.c
@@ -109,7 +109,7 @@ STATIC mp_obj_t esp32_partition_find(size_t n_args, const mp_obj_t *pos_args, mp
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_type, MP_ARG_INT, {.u_int = ESP_PARTITION_TYPE_APP} },
         { MP_QSTR_subtype, MP_ARG_INT, {.u_int = ESP_PARTITION_SUBTYPE_ANY} },
-        { MP_QSTR_label, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_label, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
diff --git a/ports/esp32/network_ppp.c b/ports/esp32/network_ppp.c
index d868450fd0..eb2181ed17 100644
--- a/ports/esp32/network_ppp.c
+++ b/ports/esp32/network_ppp.c
@@ -168,8 +168,8 @@ STATIC mp_obj_t ppp_connect_py(size_t n_args, const mp_obj_t *args, mp_map_t *kw
     enum { ARG_authmode, ARG_username, ARG_password };
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_authmode, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = PPPAUTHTYPE_NONE} },
-        { MP_QSTR_username, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-        { MP_QSTR_password, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_username, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_password, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
     };
 
     mp_arg_val_t parsed_args[MP_ARRAY_SIZE(allowed_args)];
diff --git a/ports/stm32/dac.c b/ports/stm32/dac.c
index 485829c59c..9ea6962481 100644
--- a/ports/stm32/dac.c
+++ b/ports/stm32/dac.c
@@ -229,7 +229,7 @@ STATIC void pyb_dac_print(const mp_print_t *print, mp_obj_t self_in, mp_print_ki
 STATIC mp_obj_t pyb_dac_init_helper(pyb_dac_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_bits, MP_ARG_INT, {.u_int = 8} },
-        { MP_QSTR_buffering, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_buffering, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
     };
 
     // parse args
diff --git a/ports/stm32/machine_uart.c b/ports/stm32/machine_uart.c
index 5dbc133310..0fe7b8bfa3 100644
--- a/ports/stm32/machine_uart.c
+++ b/ports/stm32/machine_uart.c
@@ -221,7 +221,7 @@ STATIC mp_obj_t pyb_uart_init_helper(pyb_uart_obj_t *self, size_t n_args, const
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_baudrate, MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = 9600} },
         { MP_QSTR_bits, MP_ARG_INT, {.u_int = 8} },
-        { MP_QSTR_parity, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_parity, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_stop, MP_ARG_INT, {.u_int = 1} },
         { MP_QSTR_flow, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = UART_HWCONTROL_NONE} },
         { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
diff --git a/ports/stm32/pin.c b/ports/stm32/pin.c
index d032d99145..55c4152bb0 100644
--- a/ports/stm32/pin.c
+++ b/ports/stm32/pin.c
@@ -329,7 +329,7 @@ STATIC MP_DEFINE_CONST_CLASSMETHOD_OBJ(pin_debug_obj, MP_ROM_PTR(&pin_debug_fun_
 STATIC mp_obj_t pin_obj_init_helper(const pin_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_mode, MP_ARG_REQUIRED | MP_ARG_INT },
-        { MP_QSTR_pull, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)}},
+        { MP_QSTR_pull, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE}},
         { MP_QSTR_af, MP_ARG_INT, {.u_int = -1}}, // legacy
         { MP_QSTR_value, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL}},
         { MP_QSTR_alt, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1}},
@@ -418,7 +418,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(pin_on_obj, pin_on);
 STATIC mp_obj_t pin_irq(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum { ARG_handler, ARG_trigger, ARG_hard };
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_handler, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_handler, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_trigger, MP_ARG_INT, {.u_int = GPIO_MODE_IT_RISING | GPIO_MODE_IT_FALLING} },
         { MP_QSTR_hard, MP_ARG_BOOL, {.u_bool = false} },
     };
diff --git a/ports/stm32/pyb_can.c b/ports/stm32/pyb_can.c
index 0de99131f0..8b58da2161 100644
--- a/ports/stm32/pyb_can.c
+++ b/ports/stm32/pyb_can.c
@@ -442,7 +442,7 @@ STATIC mp_obj_t pyb_can_recv(size_t n_args, const mp_obj_t *pos_args, mp_map_t *
     enum { ARG_fifo, ARG_list, ARG_timeout };
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_fifo,    MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = 0} },
-        { MP_QSTR_list,    MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_list,    MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_timeout, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 5000} },
     };
 
diff --git a/ports/stm32/pyb_spi.c b/ports/stm32/pyb_spi.c
index e76369973c..a3cacead24 100644
--- a/ports/stm32/pyb_spi.c
+++ b/ports/stm32/pyb_spi.c
@@ -86,7 +86,7 @@ STATIC mp_obj_t pyb_spi_init_helper(const pyb_spi_obj_t *self, size_t n_args, co
         { MP_QSTR_nss,      MP_ARG_KW_ONLY | MP_ARG_INT,  {.u_int = SPI_NSS_SOFT} },
         { MP_QSTR_firstbit, MP_ARG_KW_ONLY | MP_ARG_INT,  {.u_int = SPI_FIRSTBIT_MSB} },
         { MP_QSTR_ti,       MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
-        { MP_QSTR_crc,      MP_ARG_KW_ONLY | MP_ARG_OBJ,  {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_crc,      MP_ARG_KW_ONLY | MP_ARG_OBJ,  {.u_rom_obj = MP_ROM_NONE} },
     };
 
     // parse args
diff --git a/ports/stm32/timer.c b/ports/stm32/timer.c
index 2e8f3e05ba..feff93412f 100644
--- a/ports/stm32/timer.c
+++ b/ports/stm32/timer.c
@@ -594,13 +594,13 @@ STATIC void pyb_timer_print(const mp_print_t *print, mp_obj_t self_in, mp_print_
 STATIC mp_obj_t pyb_timer_init_helper(pyb_timer_obj_t *self, size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum { ARG_freq, ARG_prescaler, ARG_period, ARG_tick_hz, ARG_mode, ARG_div, ARG_callback, ARG_deadtime, ARG_brk };
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_freq,         MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_freq,         MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_prescaler,    MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0xffffffff} },
         { MP_QSTR_period,       MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0xffffffff} },
         { MP_QSTR_tick_hz,      MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 1000} },
         { MP_QSTR_mode,         MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = TIM_COUNTERMODE_UP} },
         { MP_QSTR_div,          MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 1} },
-        { MP_QSTR_callback,     MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_callback,     MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_deadtime,     MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
         { MP_QSTR_brk,          MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = BRK_OFF} },
     };
@@ -982,10 +982,10 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_timer_deinit_obj, pyb_timer_deinit);
 STATIC mp_obj_t pyb_timer_channel(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_mode,                MP_ARG_REQUIRED | MP_ARG_INT, {.u_int = 0} },
-        { MP_QSTR_callback,            MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-        { MP_QSTR_pin,                 MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_callback,            MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_pin,                 MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_pulse_width,         MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
-        { MP_QSTR_pulse_width_percent, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_pulse_width_percent, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_compare,             MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
         { MP_QSTR_polarity,            MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0xffffffff} },
     };
diff --git a/ports/stm32/usb.c b/ports/stm32/usb.c
index f2f3d7458a..8a4b7485bb 100644
--- a/ports/stm32/usb.c
+++ b/ports/stm32/usb.c
@@ -382,7 +382,7 @@ STATIC mp_obj_t pyb_usb_mode(size_t n_args, const mp_obj_t *pos_args, mp_map_t *
         #endif
     };
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_mode, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_mode, MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_port, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
         { MP_QSTR_vid, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = USBD_VID} },
         { MP_QSTR_pid, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = -1} },
diff --git a/ports/unix/file.c b/ports/unix/file.c
index bb841da209..6c6e26b0b2 100644
--- a/ports/unix/file.c
+++ b/ports/unix/file.c
@@ -148,10 +148,10 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(fdfile_fileno_obj, fdfile_fileno);
 // Note: encoding is ignored for now; it's also not a valid kwarg for CPython's FileIO,
 // but by adding it here we can use one single mp_arg_t array for open() and FileIO's constructor
 STATIC const mp_arg_t file_open_args[] = {
-    { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+    { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_NONE} },
     { MP_QSTR_mode, MP_ARG_OBJ, {.u_obj = MP_OBJ_NEW_QSTR(MP_QSTR_r)} },
-    { MP_QSTR_buffering, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-    { MP_QSTR_encoding, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+    { MP_QSTR_buffering, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+    { MP_QSTR_encoding, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
 };
 #define FILE_OPEN_NUM_ARGS MP_ARRAY_SIZE(file_open_args)
 
diff --git a/py/obj.h b/py/obj.h
index 7c6815a3c2..189f37d076 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -242,6 +242,10 @@ typedef union _mp_rom_obj_t { uint64_t u64; struct { const void *lo, *hi; } u32;
 
 // Macros to create objects that are stored in ROM.
 
+#ifndef MP_ROM_NONE
+#define MP_ROM_NONE MP_ROM_PTR(&mp_const_none_obj)
+#endif
+
 #ifndef MP_ROM_INT
 typedef mp_const_obj_t mp_rom_obj_t;
 #define MP_ROM_INT(i) MP_OBJ_NEW_SMALL_INT(i)
diff --git a/py/objlist.c b/py/objlist.c
index 29a1d8b1a4..00afcd56ad 100644
--- a/py/objlist.c
+++ b/py/objlist.c
@@ -312,7 +312,7 @@ STATIC void mp_quicksort(mp_obj_t *head, mp_obj_t *tail, mp_obj_t key_fn, mp_obj
 // TODO Python defines sort to be stable but ours is not
 mp_obj_t mp_obj_list_sort(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_key, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_key, MP_ARG_KW_ONLY | MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
         { MP_QSTR_reverse, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
     };
 
diff --git a/py/objproperty.c b/py/objproperty.c
index 49cb9ca1b4..2a7844b609 100644
--- a/py/objproperty.c
+++ b/py/objproperty.c
@@ -39,10 +39,10 @@ typedef struct _mp_obj_property_t {
 STATIC mp_obj_t property_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     enum { ARG_fget, ARG_fset, ARG_fdel, ARG_doc };
     static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-        { MP_QSTR_, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-        { MP_QSTR_, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
-        { MP_QSTR_doc, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
+        { MP_QSTR_doc, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
     };
     mp_arg_val_t vals[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args), allowed_args, vals);