diff --git a/py/obj.h b/py/obj.h
index 34adfbd0f0..8aa5b0a8e6 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -521,6 +521,7 @@ typedef mp_obj_t (*mp_fun_kw_t)(size_t n, const mp_obj_t *, mp_map_t *);
 //   mp_getiter_iternext_custom_t struct instance (with both .getiter and .iternext set).
 // If MP_TYPE_FLAG_ITER_IS_STREAM is set then the type implicitly gets a "return self"
 //   getiter, and mp_stream_unbuffered_iter for iternext.
+// If MP_TYPE_FLAG_INSTANCE_TYPE is set then this is an instance type (i.e. defined in Python).
 #define MP_TYPE_FLAG_NONE (0x0000)
 #define MP_TYPE_FLAG_IS_SUBCLASSED (0x0001)
 #define MP_TYPE_FLAG_HAS_SPECIAL_ACCESSORS (0x0002)
@@ -533,6 +534,7 @@ typedef mp_obj_t (*mp_fun_kw_t)(size_t n, const mp_obj_t *, mp_map_t *);
 #define MP_TYPE_FLAG_ITER_IS_ITERNEXT (0x0080)
 #define MP_TYPE_FLAG_ITER_IS_CUSTOM (0x0100)
 #define MP_TYPE_FLAG_ITER_IS_STREAM (MP_TYPE_FLAG_ITER_IS_ITERNEXT | MP_TYPE_FLAG_ITER_IS_CUSTOM)
+#define MP_TYPE_FLAG_INSTANCE_TYPE (0x0200)
 
 typedef enum {
     PRINT_STR = 0,
@@ -914,7 +916,7 @@ void *mp_obj_malloc_helper(size_t num_bytes, const mp_obj_type_t *type);
 #define mp_obj_is_int(o) (mp_obj_is_small_int(o) || mp_obj_is_exact_type(o, &mp_type_int))
 #define mp_obj_is_str(o) (mp_obj_is_qstr(o) || mp_obj_is_exact_type(o, &mp_type_str))
 #define mp_obj_is_str_or_bytes(o) (mp_obj_is_qstr(o) || (mp_obj_is_obj(o) && MP_OBJ_TYPE_GET_SLOT_OR_NULL(((mp_obj_base_t *)MP_OBJ_TO_PTR(o))->type, binary_op) == mp_obj_str_binary_op))
-#define mp_obj_is_dict_or_ordereddict(o) (mp_obj_is_obj(o) && MP_OBJ_TYPE_GET_SLOT_OR_NULL(((mp_obj_base_t *)MP_OBJ_TO_PTR(o))->type, make_new) == mp_obj_dict_make_new)
+bool mp_obj_is_dict_or_ordereddict(mp_obj_t o);
 #define mp_obj_is_fun(o) (mp_obj_is_obj(o) && (((mp_obj_base_t *)MP_OBJ_TO_PTR(o))->type->name == MP_QSTR_function))
 
 mp_obj_t mp_obj_new_type(qstr name, mp_obj_t bases_tuple, mp_obj_t locals_dict);
@@ -1030,7 +1032,7 @@ mp_int_t mp_obj_int_get_checked(mp_const_obj_t self_in);
 mp_uint_t mp_obj_int_get_uint_checked(mp_const_obj_t self_in);
 
 // exception
-#define mp_obj_is_native_exception_instance(o) (MP_OBJ_TYPE_GET_SLOT_OR_NULL(mp_obj_get_type(o), make_new) == mp_obj_exception_make_new)
+bool mp_obj_is_native_exception_instance(mp_obj_t self_in);
 bool mp_obj_is_exception_type(mp_obj_t self_in);
 bool mp_obj_is_exception_instance(mp_obj_t self_in);
 bool mp_obj_exception_match(mp_obj_t exc, mp_const_obj_t exc_type);
diff --git a/py/objdict.c b/py/objdict.c
index 68c33961c7..7fad5fc8f4 100644
--- a/py/objdict.c
+++ b/py/objdict.c
@@ -33,6 +33,10 @@
 #include "py/objtype.h"
 #include "py/objstr.h"
 
+bool mp_obj_is_dict_or_ordereddict(mp_obj_t o) {
+    return mp_obj_is_obj(o) && MP_OBJ_TYPE_GET_SLOT_OR_NULL(((mp_obj_base_t *)MP_OBJ_TO_PTR(o))->type, make_new) == mp_obj_dict_make_new;
+}
+
 const mp_obj_dict_t mp_const_empty_dict_obj = {
     .base = { .type = &mp_type_dict },
     .map = {
diff --git a/py/objexcept.c b/py/objexcept.c
index 3b76ae62cc..515cbe7425 100644
--- a/py/objexcept.c
+++ b/py/objexcept.c
@@ -111,6 +111,10 @@ mp_obj_t mp_alloc_emergency_exception_buf(mp_obj_t size_in) {
 #endif
 #endif  // MICROPY_ENABLE_EMERGENCY_EXCEPTION_BUF
 
+bool mp_obj_is_native_exception_instance(mp_obj_t self_in) {
+    return MP_OBJ_TYPE_GET_SLOT_OR_NULL(mp_obj_get_type(self_in), make_new) == mp_obj_exception_make_new;
+}
+
 STATIC mp_obj_exception_t *get_native_exception(mp_obj_t self_in) {
     assert(mp_obj_is_exception_instance(self_in));
     if (mp_obj_is_native_exception_instance(self_in)) {
diff --git a/py/objstr.c b/py/objstr.c
index 50ab0018ed..62d7bfb4cc 100644
--- a/py/objstr.c
+++ b/py/objstr.c
@@ -63,6 +63,10 @@ STATIC void str_check_arg_type(const mp_obj_type_t *self_type, const mp_obj_t ar
     }
 }
 
+STATIC void check_is_str_or_bytes(mp_obj_t self_in) {
+    mp_check_self(mp_obj_is_str_or_bytes(self_in));
+}
+
 /******************************************************************************/
 /* str                                                                        */
 
@@ -468,7 +472,7 @@ STATIC mp_obj_t bytes_subscr(mp_obj_t self_in, mp_obj_t index, mp_obj_t value) {
 }
 
 STATIC mp_obj_t str_join(mp_obj_t self_in, mp_obj_t arg) {
-    mp_check_self(mp_obj_is_str_or_bytes(self_in));
+    check_is_str_or_bytes(self_in);
     const mp_obj_type_t *self_type = mp_obj_get_type(self_in);
     const mp_obj_type_t *ret_type = self_type;
 
@@ -724,7 +728,7 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_rsplit_obj, 1, 3, str_rsplit);
 
 STATIC mp_obj_t str_finder(size_t n_args, const mp_obj_t *args, int direction, bool is_index) {
     const mp_obj_type_t *self_type = mp_obj_get_type(args[0]);
-    mp_check_self(mp_obj_is_str_or_bytes(args[0]));
+    check_is_str_or_bytes(args[0]);
 
     // check argument type
     str_check_arg_type(self_type, args[1]);
@@ -820,7 +824,7 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_endswith_obj, 2, 3, str_endswith);
 enum { LSTRIP, RSTRIP, STRIP };
 
 STATIC mp_obj_t str_uni_strip(int type, size_t n_args, const mp_obj_t *args) {
-    mp_check_self(mp_obj_is_str_or_bytes(args[0]));
+    check_is_str_or_bytes(args[0]);
     const mp_obj_type_t *self_type = mp_obj_get_type(args[0]);
 
     const byte *chars_to_del;
@@ -1422,7 +1426,7 @@ STATIC vstr_t mp_obj_str_format_helper(const char *str, const char *top, int *ar
 }
 
 mp_obj_t mp_obj_str_format(size_t n_args, const mp_obj_t *args, mp_map_t *kwargs) {
-    mp_check_self(mp_obj_is_str_or_bytes(args[0]));
+    check_is_str_or_bytes(args[0]);
 
     GET_STR_DATA_LEN(args[0], str, len);
     int arg_i = 0;
@@ -1433,7 +1437,7 @@ MP_DEFINE_CONST_FUN_OBJ_KW(str_format_obj, 1, mp_obj_str_format);
 
 #if MICROPY_PY_BUILTINS_STR_OP_MODULO
 STATIC mp_obj_t str_modulo_format(mp_obj_t pattern, size_t n_args, const mp_obj_t *args, mp_obj_t dict) {
-    mp_check_self(mp_obj_is_str_or_bytes(pattern));
+    check_is_str_or_bytes(pattern);
 
     GET_STR_DATA_LEN(pattern, str, len);
     #if MICROPY_ERROR_REPORTING > MICROPY_ERROR_REPORTING_TERSE
@@ -1639,7 +1643,7 @@ STATIC mp_obj_t str_modulo_format(mp_obj_t pattern, size_t n_args, const mp_obj_
 // The implementation is optimized, returning the original string if there's
 // nothing to replace.
 STATIC mp_obj_t str_replace(size_t n_args, const mp_obj_t *args) {
-    mp_check_self(mp_obj_is_str_or_bytes(args[0]));
+    check_is_str_or_bytes(args[0]);
 
     mp_int_t max_rep = -1;
     if (n_args == 4) {
@@ -1742,7 +1746,7 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_replace_obj, 3, 4, str_replace);
 #if MICROPY_PY_BUILTINS_STR_COUNT
 STATIC mp_obj_t str_count(size_t n_args, const mp_obj_t *args) {
     const mp_obj_type_t *self_type = mp_obj_get_type(args[0]);
-    mp_check_self(mp_obj_is_str_or_bytes(args[0]));
+    check_is_str_or_bytes(args[0]);
 
     // check argument type
     str_check_arg_type(self_type, args[1]);
@@ -1782,7 +1786,7 @@ MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(str_count_obj, 2, 4, str_count);
 
 #if MICROPY_PY_BUILTINS_STR_PARTITION
 STATIC mp_obj_t str_partitioner(mp_obj_t self_in, mp_obj_t arg, int direction) {
-    mp_check_self(mp_obj_is_str_or_bytes(self_in));
+    check_is_str_or_bytes(self_in);
     const mp_obj_type_t *self_type = mp_obj_get_type(self_in);
     str_check_arg_type(self_type, arg);
 
diff --git a/py/objtype.c b/py/objtype.c
index db364e0e5a..909fc83393 100644
--- a/py/objtype.c
+++ b/py/objtype.c
@@ -277,7 +277,7 @@ STATIC void instance_print(const mp_print_t *print, mp_obj_t self_in, mp_print_k
     mp_printf(print, "<%s object at %p>", mp_obj_get_type_str(self_in), self);
 }
 
-mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+STATIC mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     assert(mp_obj_is_instance_type(self));
 
     // look for __new__ function
@@ -1131,7 +1131,8 @@ mp_obj_t mp_obj_new_type(qstr name, mp_obj_t bases_tuple, mp_obj_t locals_dict)
     uint16_t base_flags = MP_TYPE_FLAG_EQ_NOT_REFLEXIVE
         | MP_TYPE_FLAG_EQ_CHECKS_OTHER_TYPE
         | MP_TYPE_FLAG_EQ_HAS_NEQ_TEST
-        | MP_TYPE_FLAG_ITER_IS_GETITER;
+        | MP_TYPE_FLAG_ITER_IS_GETITER
+        | MP_TYPE_FLAG_INSTANCE_TYPE;
     size_t bases_len;
     mp_obj_t *bases_items;
     mp_obj_tuple_get(bases_tuple, &bases_len, &bases_items);
diff --git a/py/objtype.h b/py/objtype.h
index 76a290760c..839cc6d146 100644
--- a/py/objtype.h
+++ b/py/objtype.h
@@ -46,10 +46,8 @@ mp_obj_instance_t *mp_obj_new_instance(const mp_obj_type_t *cls, const mp_obj_ty
 bool mp_obj_instance_is_callable(mp_obj_t self_in);
 mp_obj_t mp_obj_instance_call(mp_obj_t self_in, size_t n_args, size_t n_kw, const mp_obj_t *args);
 
-#define mp_obj_is_instance_type(type) (MP_OBJ_TYPE_GET_SLOT_OR_NULL(type, make_new) == mp_obj_instance_make_new)
-#define mp_obj_is_native_type(type) (MP_OBJ_TYPE_GET_SLOT_OR_NULL(type, make_new) != mp_obj_instance_make_new)
-// this needs to be exposed for the above macros to work correctly
-mp_obj_t mp_obj_instance_make_new(const mp_obj_type_t *self_in, size_t n_args, size_t n_kw, const mp_obj_t *args);
+#define mp_obj_is_instance_type(type) ((type)->flags & MP_TYPE_FLAG_INSTANCE_TYPE)
+#define mp_obj_is_native_type(type) (!((type)->flags & MP_TYPE_FLAG_INSTANCE_TYPE))
 
 // this needs to be exposed for mp_getiter
 mp_obj_t mp_obj_instance_getiter(mp_obj_t self_in, mp_obj_iter_buf_t *iter_buf);