diff --git a/tests/io/open_append.py b/tests/io/open_append.py
index da420a16ea72122fae3c20103cc305dcc3d6ab76..2120b72f04283358d703d58c8da3bc7d00eca3d3 100644
--- a/tests/io/open_append.py
+++ b/tests/io/open_append.py
@@ -1,6 +1,6 @@
 import sys
 try:
-    import _os as os
+    import uos as os
 except ImportError:
     import os
 
diff --git a/tests/run-tests-exp.py b/tests/run-tests-exp.py
index a4ac26dba2a5e0cea3efce72149803e174785043..3af8feae7c7138e4f14f4ea19745101370027b3d 100644
--- a/tests/run-tests-exp.py
+++ b/tests/run-tests-exp.py
@@ -6,7 +6,7 @@
 # which is to be tested, so should use minimal language functionality.
 #
 import sys
-import _os as os
+import uos as os
 
 
 tests = [
diff --git a/unix/modos.c b/unix/modos.c
index faf33dac9cb25bb995b296743fa7e7cc5cebc349..f681acaff274d8f1eb241e923d2171414d264f28 100644
--- a/unix/modos.c
+++ b/unix/modos.c
@@ -156,7 +156,7 @@ STATIC mp_obj_t mod_os_mkdir(mp_obj_t path_in) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_os_mkdir_obj, mod_os_mkdir);
 
 STATIC const mp_rom_map_elem_t mp_module_os_globals_table[] = {
-    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR__os) },
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_uos) },
     { MP_ROM_QSTR(MP_QSTR_stat), MP_ROM_PTR(&mod_os_stat_obj) },
     #if MICROPY_PY_OS_STATVFS
     { MP_ROM_QSTR(MP_QSTR_statvfs), MP_ROM_PTR(&mod_os_statvfs_obj) },
@@ -171,6 +171,6 @@ STATIC MP_DEFINE_CONST_DICT(mp_module_os_globals, mp_module_os_globals_table);
 
 const mp_obj_module_t mp_module_os = {
     .base = { &mp_type_module },
-    .name = MP_QSTR__os,
+    .name = MP_QSTR_uos,
     .globals = (mp_obj_dict_t*)&mp_module_os_globals,
 };
diff --git a/unix/mpconfigport.h b/unix/mpconfigport.h
index 7a4b6e523ec230c6379c603500f4b7d647ad4093..d85b98b8dc567e80e1fecdba068767035f54f7f1 100644
--- a/unix/mpconfigport.h
+++ b/unix/mpconfigport.h
@@ -163,7 +163,7 @@ extern const struct _mp_obj_module_t mp_module_jni;
     MICROPY_PY_JNI_DEF \
     MICROPY_PY_TIME_DEF \
     MICROPY_PY_SOCKET_DEF \
-    { MP_ROM_QSTR(MP_QSTR__os), MP_ROM_PTR(&mp_module_os) }, \
+    { MP_ROM_QSTR(MP_QSTR_uos), MP_ROM_PTR(&mp_module_os) }, \
     { MP_ROM_QSTR(MP_QSTR_uselect), MP_ROM_PTR(&mp_module_uselect) }, \
     MICROPY_PY_TERMIOS_DEF \
 
diff --git a/unix/mpconfigport_minimal.h b/unix/mpconfigport_minimal.h
index 09d5fbf6d33be32566e99ebc8d2fd8319a0fb670..cffc9a6250b3f36f354d5a1d87f99152bffd8ed3 100644
--- a/unix/mpconfigport_minimal.h
+++ b/unix/mpconfigport_minimal.h
@@ -98,7 +98,7 @@
 extern const struct _mp_obj_module_t mp_module_os;
 
 #define MICROPY_PORT_BUILTIN_MODULES \
-    { MP_OBJ_NEW_QSTR(MP_QSTR__os), (mp_obj_t)&mp_module_os }, \
+    { MP_OBJ_NEW_QSTR(MP_QSTR_uos), (mp_obj_t)&mp_module_os }, \
 
 // type definitions for the specific machine
 
diff --git a/unix/qstrdefsport.h b/unix/qstrdefsport.h
index f6ba9e4106fcf35cbf54cbdb2dc88dce438e343a..7323b97a4d986927ece57b0a4a93b68f0616d831 100644
--- a/unix/qstrdefsport.h
+++ b/unix/qstrdefsport.h
@@ -34,7 +34,7 @@ Q(makefile)
 Q(FileIO)
 Q(flush)
 
-Q(_os)
+Q(uos)
 Q(stat)
 #if MICROPY_PY_OS_STATVFS
 Q(statvfs)
diff --git a/windows/mpconfigport.h b/windows/mpconfigport.h
index 4b13fedad2616cc3343de11a550a89f905f033ef..5f0b34f57b6966d64d117c05cb958bb0b2163cff 100644
--- a/windows/mpconfigport.h
+++ b/windows/mpconfigport.h
@@ -152,7 +152,7 @@ extern const struct _mp_obj_module_t mp_module_os;
 extern const struct _mp_obj_module_t mp_module_time;
 #define MICROPY_PORT_BUILTIN_MODULES \
     { MP_OBJ_NEW_QSTR(MP_QSTR_utime), (mp_obj_t)&mp_module_time }, \
-    { MP_OBJ_NEW_QSTR(MP_QSTR__os), (mp_obj_t)&mp_module_os }, \
+    { MP_OBJ_NEW_QSTR(MP_QSTR_uos), (mp_obj_t)&mp_module_os }, \
 
 #if MICROPY_USE_READLINE == 1
 #define MICROPY_PORT_ROOT_POINTERS \