diff --git a/py/modsys.c b/py/modsys.c
index f2b87a68cf..d133d6b278 100644
--- a/py/modsys.c
+++ b/py/modsys.c
@@ -55,8 +55,10 @@ STATIC const MP_DEFINE_STR_OBJ(version_obj, "3.4.0");
 
 STATIC const mp_map_elem_t mp_module_sys_globals_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR___name__), MP_OBJ_NEW_QSTR(MP_QSTR_sys) },
+#if MICROPY_SYS_EXIT
     // Should be implemented by port
     { MP_OBJ_NEW_QSTR(MP_QSTR_exit), (mp_obj_t)&mp_sys_exit_obj },
+#endif
 
     { MP_OBJ_NEW_QSTR(MP_QSTR_path), (mp_obj_t)&mp_sys_path_obj },
     { MP_OBJ_NEW_QSTR(MP_QSTR_argv), (mp_obj_t)&mp_sys_argv_obj },
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 2711318d1f..73ecc92d16 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -229,6 +229,11 @@ typedef double mp_float_t;
 #define MICROPY_MOD_SYS_STDFILES (0)
 #endif
 
+// sys.exit() availability
+#ifndef MICROPY_SYS_EXIT
+#define MICROPY_SYS_EXIT (0)
+#endif
+
 // Whether to support slice object and correspondingly
 // slice subscript operators
 #ifndef MICROPY_ENABLE_SLICE
diff --git a/stmhal/mpconfigport.h b/stmhal/mpconfigport.h
index 0a99128bf0..43ef27f874 100644
--- a/stmhal/mpconfigport.h
+++ b/stmhal/mpconfigport.h
@@ -45,6 +45,7 @@
 #define MICROPY_ENABLE_LFN          (1)
 #define MICROPY_LFN_CODE_PAGE       (437) /* 1=SFN/ANSI 437=LFN/U.S.(OEM) */
 #define MICROPY_MOD_SYS_STDFILES    (1)
+#define MICROPY_SYS_EXIT            (1)
 #define MICROPY_ENABLE_MOD_CMATH    (1)
 
 // extra built in names to add to the global namespace
diff --git a/unix/mpconfigport.h b/unix/mpconfigport.h
index ba95349a6e..38bb979c92 100644
--- a/unix/mpconfigport.h
+++ b/unix/mpconfigport.h
@@ -44,6 +44,7 @@
 #define MICROPY_USE_COMPUTED_GOTO   (1)
 #define MICROPY_MOD_SYS_STDFILES    (1)
 #define MICROPY_ENABLE_MOD_CMATH    (1)
+#define MICROPY_SYS_EXIT            (1)
 // Define to MICROPY_ERROR_REPORTING_DETAILED to get function, etc.
 // names in exception messages (may require more RAM).
 #define MICROPY_ERROR_REPORTING     (MICROPY_ERROR_REPORTING_DETAILED)