diff --git a/ports/nrf/builtin_open.c b/ports/nrf/builtin_open.c
deleted file mode 100644
index 697eec8eaa..0000000000
--- a/ports/nrf/builtin_open.c
+++ /dev/null
@@ -1,30 +0,0 @@
-/*
- * This file is part of the MicroPython project, http://micropython.org/
- *
- * The MIT License (MIT)
- *
- * Copyright (c) 2013, 2014 Damien P. George
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-#include "py/runtime.h"
-#include "extmod/vfs_fat_file.h"
-
-MP_DEFINE_CONST_FUN_OBJ_KW(mp_builtin_open_obj, 1, fatfs_builtin_open);
diff --git a/ports/nrf/main.c b/ports/nrf/main.c
index 262573d5ff..92f578cda1 100644
--- a/ports/nrf/main.c
+++ b/ports/nrf/main.c
@@ -30,6 +30,7 @@
 #include <string.h>
 
 #include "py/nlr.h"
+#include "py/mperrno.h"
 #include "py/lexer.h"
 #include "py/parse.h"
 #include "py/obj.h"
@@ -213,6 +214,21 @@ pin_init0();
     return 0;
 }
 
+#if !MICROPY_VFS
+mp_lexer_t *mp_lexer_new_from_file(const char *filename) {
+    mp_raise_OSError(MP_ENOENT);
+}
+
+mp_import_stat_t mp_import_stat(const char *path) {
+    return MP_IMPORT_STAT_NO_EXIST;
+}
+
+STATIC mp_obj_t mp_builtin_open(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
+    mp_raise_OSError(MP_EPERM);
+}
+MP_DEFINE_CONST_FUN_OBJ_KW(mp_builtin_open_obj, 1, mp_builtin_open);
+#endif
+
 void HardFault_Handler(void)
 {
 #if NRF52
diff --git a/ports/nrf/modules/uos/moduos.c b/ports/nrf/modules/uos/moduos.c
index 84671bc59d..21ea2cde67 100644
--- a/ports/nrf/modules/uos/moduos.c
+++ b/ports/nrf/modules/uos/moduos.c
@@ -79,6 +79,7 @@ STATIC mp_obj_t os_uname(void) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_0(os_uname_obj, os_uname);
 
+#if MICROPY_VFS
 /// \function sync()
 /// Sync all filesystems.
 STATIC mp_obj_t os_sync(void) {
@@ -89,6 +90,7 @@ STATIC mp_obj_t os_sync(void) {
     return mp_const_none;
 }
 MP_DEFINE_CONST_FUN_OBJ_0(mod_os_sync_obj, os_sync);
+#endif
 
 #if MICROPY_HW_ENABLE_RNG
 /// \function urandom(n)
@@ -133,6 +135,7 @@ STATIC const mp_rom_map_elem_t os_module_globals_table[] = {
 
     { MP_ROM_QSTR(MP_QSTR_uname), MP_ROM_PTR(&os_uname_obj) },
 
+#if MICROPY_VFS
     { MP_ROM_QSTR(MP_QSTR_chdir), MP_ROM_PTR(&mp_vfs_chdir_obj) },
     { MP_ROM_QSTR(MP_QSTR_getcwd), MP_ROM_PTR(&mp_vfs_getcwd_obj) },
     { MP_ROM_QSTR(MP_QSTR_listdir), MP_ROM_PTR(&mp_vfs_listdir_obj) },
@@ -145,6 +148,7 @@ STATIC const mp_rom_map_elem_t os_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_unlink), MP_ROM_PTR(&mp_vfs_remove_obj) }, // unlink aliases to remove
 
     { MP_ROM_QSTR(MP_QSTR_sync), MP_ROM_PTR(&mod_os_sync_obj) },
+#endif
 
     /// \constant sep - separation character used in paths
     { MP_ROM_QSTR(MP_QSTR_sep), MP_ROM_QSTR(MP_QSTR__slash_) },
@@ -155,9 +159,11 @@ STATIC const mp_rom_map_elem_t os_module_globals_table[] = {
 
     // these are MicroPython extensions
     { MP_ROM_QSTR(MP_QSTR_dupterm), MP_ROM_PTR(&mod_os_dupterm_obj) },
+#if MICROPY_VFS
     { MP_ROM_QSTR(MP_QSTR_mount), MP_ROM_PTR(&mp_vfs_mount_obj) },
     { MP_ROM_QSTR(MP_QSTR_umount), MP_ROM_PTR(&mp_vfs_umount_obj) },
     { MP_ROM_QSTR(MP_QSTR_VfsFat), MP_ROM_PTR(&mp_fat_vfs_type) },
+#endif
 };
 
 STATIC MP_DEFINE_CONST_DICT(os_module_globals, os_module_globals_table);
diff --git a/ports/nrf/mpconfigport.h b/ports/nrf/mpconfigport.h
index bc924d514c..46ad669119 100644
--- a/ports/nrf/mpconfigport.h
+++ b/ports/nrf/mpconfigport.h
@@ -30,13 +30,17 @@
 #include <mpconfigboard.h>
 
 // options to control how MicroPython is built
+#ifndef MICROPY_VFS
+#define MICROPY_VFS                 (1)
+#endif
+#define MICROPY_VFS_FAT             (MICROPY_VFS)
 #define MICROPY_ALLOC_PATH_MAX      (512)
 #define MICROPY_PERSISTENT_CODE_LOAD (0)
 #define MICROPY_EMIT_THUMB          (0)
 #define MICROPY_EMIT_INLINE_THUMB   (0)
 #define MICROPY_COMP_MODULE_CONST   (0)
 #define MICROPY_COMP_TRIPLE_TUPLE_ASSIGN (0)
-#define MICROPY_READER_VFS          (1)
+#define MICROPY_READER_VFS          (MICROPY_VFS)
 #define MICROPY_ENABLE_GC           (1)
 #define MICROPY_ENABLE_FINALISER    (1)
 #define MICROPY_STACK_CHECK         (0)
@@ -54,8 +58,6 @@
 #define MICROPY_OPT_COMPUTED_GOTO   (0)
 #define MICROPY_OPT_CACHE_MAP_LOOKUP_IN_BYTECODE (0)
 #define MICROPY_OPT_MPZ_BITWISE     (0)
-#define MICROPY_VFS                 (1)
-#define MICROPY_VFS_FAT             (1)
 
 // fatfs configuration used in ffconf.h
 #define MICROPY_FATFS_ENABLE_LFN       (1)
@@ -69,9 +71,11 @@
 #define mp_type_textio fatfs_type_textio
 
 // use vfs's functions for import stat and builtin open
+#if MICROPY_VFS
 #define mp_import_stat mp_vfs_import_stat
 #define mp_builtin_open mp_vfs_open
 #define mp_builtin_open_obj mp_vfs_open_obj
+#endif
 
 #define MICROPY_STREAMS_NON_BLOCK   (1)
 #define MICROPY_MODULE_WEAK_LINKS   (1)