diff --git a/ports/atmel-samd/mpconfigport.h b/ports/atmel-samd/mpconfigport.h
index ee75a26c5b..276ffafe38 100644
--- a/ports/atmel-samd/mpconfigport.h
+++ b/ports/atmel-samd/mpconfigport.h
@@ -292,6 +292,18 @@ extern const struct _mp_obj_module_t usb_hid_module;
     { MP_OBJ_NEW_QSTR(MP_QSTR_uheap),(mp_obj_t)&uheap_module }, \
     { MP_OBJ_NEW_QSTR(MP_QSTR_ustack),(mp_obj_t)&ustack_module }
 
+#define MICROPY_PY_UERRNO_LIST \
+    X(EPERM) \
+    X(ENOENT) \
+    X(EIO) \
+    X(EAGAIN) \
+    X(ENOMEM) \
+    X(EACCES) \
+    X(EEXIST) \
+    X(ENODEV) \
+    X(EISDIR) \
+    X(EINVAL) \
+
 // We need to provide a declaration/definition of alloca()
 #include <alloca.h>
 
diff --git a/ports/nrf/mpconfigport.h b/ports/nrf/mpconfigport.h
index 442e98de53..e379469c08 100644
--- a/ports/nrf/mpconfigport.h
+++ b/ports/nrf/mpconfigport.h
@@ -82,7 +82,7 @@
 #define MICROPY_STREAMS_NON_BLOCK                (1)
 #define MICROPY_MODULE_WEAK_LINKS                (1)
 #define MICROPY_CAN_OVERRIDE_BUILTINS            (1)
-#define MICROPY_USE_INTERNAL_ERRNO               (1)
+#define MICROPY_USE_INTERNAL_ERRNO               (0)
 #define MICROPY_PY_FUNCTION_ATTRS                (1)
 #define MICROPY_PY_BUILTINS_STR_UNICODE          (1)
 #define MICROPY_PY_BUILTINS_STR_CENTER           (0)
diff --git a/py/moduerrno.c b/py/moduerrno.c
index ce8a6bf89e..660fca07a2 100644
--- a/py/moduerrno.c
+++ b/py/moduerrno.c
@@ -30,8 +30,6 @@
 #include "py/obj.h"
 #include "py/mperrno.h"
 
-#if MICROPY_PY_UERRNO
-
 // This list can be defined per port in mpconfigport.h to tailor it to a
 // specific port's needs.  If it's not defined then we provide a default.
 #ifndef MICROPY_PY_UERRNO_LIST
@@ -61,6 +59,8 @@
 
 #endif
 
+#if MICROPY_PY_UERRNO
+
 #if MICROPY_PY_UERRNO_ERRORCODE
 STATIC const mp_rom_map_elem_t errorcode_table[] = {
     #define X(e) { MP_ROM_INT(MP_ ## e), MP_ROM_QSTR(MP_QSTR_## e) },
@@ -133,4 +133,15 @@ qstr mp_errno_to_str(mp_obj_t errno_val) {
     #endif
 }
 
+#else //MICROPY_PY_UERRNO
+
+qstr mp_errno_to_str(mp_obj_t errno_val) {
+    int v = MP_OBJ_SMALL_INT_VALUE(errno_val);
+    #define X(e) if (v == e) return (MP_QSTR_ ## e);
+    MICROPY_PY_UERRNO_LIST
+    #undef X
+
+    return MP_QSTR_;
+}
+
 #endif //MICROPY_PY_UERRNO
diff --git a/py/mperrno.h b/py/mperrno.h
index caac116ab6..a028157ba7 100644
--- a/py/mperrno.h
+++ b/py/mperrno.h
@@ -142,12 +142,6 @@
 
 #endif
 
-#if MICROPY_PY_UERRNO
-
-#include "py/obj.h"
-
 qstr mp_errno_to_str(mp_obj_t errno_val);
 
-#endif
-
 #endif // MICROPY_INCLUDED_PY_MPERRNO_H
diff --git a/py/objexcept.c b/py/objexcept.c
index a800a13fb1..f0874df773 100644
--- a/py/objexcept.c
+++ b/py/objexcept.c
@@ -113,7 +113,6 @@ STATIC void mp_obj_exception_print(const mp_print_t *print, mp_obj_t o_in, mp_pr
             mp_print_str(print, "");
             return;
         } else if (o->args->len == 1) {
-            #if MICROPY_PY_UERRNO
             // try to provide a nice OSError error message
             if (o->base.type == &mp_type_OSError && MP_OBJ_IS_SMALL_INT(o->args->items[0])) {
                 qstr qst = mp_errno_to_str(o->args->items[0]);
@@ -122,7 +121,6 @@ STATIC void mp_obj_exception_print(const mp_print_t *print, mp_obj_t o_in, mp_pr
                     return;
                 }
             }
-            #endif
             mp_obj_print_helper(print, o->args->items[0], PRINT_STR);
             return;
         }