diff --git a/ports/nrf/main.c b/ports/nrf/main.c
index 8e57be8dec..bcd0bb9d71 100644
--- a/ports/nrf/main.c
+++ b/ports/nrf/main.c
@@ -171,7 +171,7 @@ soft_reset:
             MP_OBJ_NEW_SMALL_INT(0),
             MP_OBJ_NEW_SMALL_INT(115200),
         };
-        MP_STATE_PORT(board_stdio_uart) = MP_OBJ_TYPE_GET_SLOT(&machine_uart_type, make_new)((mp_obj_t)&machine_uart_type, MP_ARRAY_SIZE(args), 0, args);
+        MP_STATE_VM(dupterm_objs[0]) = MP_OBJ_TYPE_GET_SLOT(&machine_uart_type, make_new)((mp_obj_t)&machine_uart_type, MP_ARRAY_SIZE(args), 0, args);
     }
     #endif
 
diff --git a/ports/nrf/modules/os/modos.c b/ports/nrf/modules/os/modos.c
index ebe5045515..6ff7200a12 100644
--- a/ports/nrf/modules/os/modos.c
+++ b/ports/nrf/modules/os/modos.c
@@ -118,16 +118,16 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_1(os_urandom_obj, os_urandom);
 // TODO should accept any object with read/write methods.
 STATIC mp_obj_t os_dupterm(mp_uint_t n_args, const mp_obj_t *args) {
     if (n_args == 0) {
-        if (MP_STATE_PORT(board_stdio_uart) == NULL) {
+        if (MP_STATE_VM(dupterm_objs[0]) == MP_OBJ_NULL) {
             return mp_const_none;
         } else {
-            return MP_STATE_PORT(board_stdio_uart);
+            return MP_STATE_VM(dupterm_objs[0]);
         }
     } else {
         if (args[0] == mp_const_none) {
-            MP_STATE_PORT(board_stdio_uart) = NULL;
+            MP_STATE_VM(dupterm_objs[0]) = MP_OBJ_NULL;
         } else if (mp_obj_get_type(args[0]) == &machine_uart_type) {
-            MP_STATE_PORT(board_stdio_uart) = args[0];
+            MP_STATE_VM(dupterm_objs[0]) = args[0];
         } else {
             mp_raise_ValueError(MP_ERROR_TEXT("need a UART object"));
         }
diff --git a/ports/nrf/mpconfigport.h b/ports/nrf/mpconfigport.h
index 264b0dfe8d..85db263648 100644
--- a/ports/nrf/mpconfigport.h
+++ b/ports/nrf/mpconfigport.h
@@ -135,6 +135,7 @@
 
 // Use port specific os module rather than extmod variant.
 #define MICROPY_PY_OS               (0)
+#define MICROPY_PY_OS_DUPTERM       (1)
 
 #define MICROPY_STREAMS_NON_BLOCK   (1)
 #define MICROPY_CAN_OVERRIDE_BUILTINS (1)
diff --git a/ports/nrf/mphalport.c b/ports/nrf/mphalport.c
index 7a51e187b7..f6c934a8b5 100644
--- a/ports/nrf/mphalport.c
+++ b/ports/nrf/mphalport.c
@@ -175,11 +175,11 @@ void mp_hal_set_interrupt_char(int c) {
 #if !MICROPY_PY_BLE_NUS && !MICROPY_HW_USB_CDC
 uintptr_t mp_hal_stdio_poll(uintptr_t poll_flags) {
     uintptr_t ret = 0;
-    if ((poll_flags & MP_STREAM_POLL_RD) && MP_STATE_PORT(board_stdio_uart) != NULL
-        && uart_rx_any(MP_STATE_PORT(board_stdio_uart))) {
+    if ((poll_flags & MP_STREAM_POLL_RD) && MP_STATE_VM(dupterm_objs[0]) != MP_OBJ_NULL
+        && uart_rx_any(MP_STATE_VM(dupterm_objs[0]))) {
         ret |= MP_STREAM_POLL_RD;
     }
-    if ((poll_flags & MP_STREAM_POLL_WR) && MP_STATE_PORT(board_stdio_uart) != NULL) {
+    if ((poll_flags & MP_STREAM_POLL_WR) && MP_STATE_VM(dupterm_objs[0]) != MP_OBJ_NULL) {
         ret |= MP_STREAM_POLL_WR;
     }
     return ret;
@@ -187,8 +187,8 @@ uintptr_t mp_hal_stdio_poll(uintptr_t poll_flags) {
 
 int mp_hal_stdin_rx_chr(void) {
     for (;;) {
-        if (MP_STATE_PORT(board_stdio_uart) != NULL && uart_rx_any(MP_STATE_PORT(board_stdio_uart))) {
-            return uart_rx_char(MP_STATE_PORT(board_stdio_uart));
+        if (MP_STATE_VM(dupterm_objs[0]) != MP_OBJ_NULL && uart_rx_any(MP_STATE_VM(dupterm_objs[0]))) {
+            return uart_rx_char(MP_STATE_VM(dupterm_objs[0]));
         }
         MICROPY_EVENT_POLL_HOOK
     }
@@ -197,14 +197,14 @@ int mp_hal_stdin_rx_chr(void) {
 }
 
 void mp_hal_stdout_tx_strn(const char *str, mp_uint_t len) {
-    if (MP_STATE_PORT(board_stdio_uart) != NULL) {
-        uart_tx_strn(MP_STATE_PORT(board_stdio_uart), str, len);
+    if (MP_STATE_VM(dupterm_objs[0]) != MP_OBJ_NULL) {
+        uart_tx_strn(MP_STATE_VM(dupterm_objs[0]), str, len);
     }
 }
 
 void mp_hal_stdout_tx_strn_cooked(const char *str, mp_uint_t len) {
-    if (MP_STATE_PORT(board_stdio_uart) != NULL) {
-        uart_tx_strn_cooked(MP_STATE_PORT(board_stdio_uart), str, len);
+    if (MP_STATE_VM(dupterm_objs[0]) != MP_OBJ_NULL) {
+        uart_tx_strn_cooked(MP_STATE_VM(dupterm_objs[0]), str, len);
     }
 }
 #endif
@@ -377,5 +377,3 @@ const char *nrfx_error_code_lookup(uint32_t err_code) {
 }
 
 #endif // NRFX_LOG_ENABLED
-
-MP_REGISTER_ROOT_POINTER(struct _machine_uart_obj_t *board_stdio_uart);