diff --git a/py/obj.h b/py/obj.h
index 1b926ce14..1169a9095 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -607,7 +607,7 @@ static inline mp_obj_t mp_obj_new_bool(mp_int_t x) { return x ? mp_const_true :
 mp_obj_t mp_obj_new_cell(mp_obj_t obj);
 mp_obj_t mp_obj_new_int(mp_int_t value);
 mp_obj_t mp_obj_new_int_from_uint(mp_uint_t value);
-mp_obj_t mp_obj_new_int_from_str_len(const char **str, mp_uint_t len, bool neg, mp_uint_t base);
+mp_obj_t mp_obj_new_int_from_str_len(const char **str, size_t len, bool neg, unsigned int base);
 mp_obj_t mp_obj_new_int_from_ll(long long val); // this must return a multi-precision integer object (or raise an overflow exception)
 mp_obj_t mp_obj_new_int_from_ull(unsigned long long val); // this must return a multi-precision integer object (or raise an overflow exception)
 mp_obj_t mp_obj_new_str(const char* data, size_t len, bool make_qstr_if_not_already);
diff --git a/py/objint.c b/py/objint.c
index 222aa1de7..2a7e3f3fd 100644
--- a/py/objint.c
+++ b/py/objint.c
@@ -291,7 +291,7 @@ mp_obj_t mp_obj_int_binary_op(mp_uint_t op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
 }
 
 // This is called only with strings whose value doesn't fit in SMALL_INT
-mp_obj_t mp_obj_new_int_from_str_len(const char **str, mp_uint_t len, bool neg, mp_uint_t base) {
+mp_obj_t mp_obj_new_int_from_str_len(const char **str, size_t len, bool neg, unsigned int base) {
     mp_raise_msg(&mp_type_OverflowError, "long int not supported in this build");
     return mp_const_none;
 }
diff --git a/py/objint_longlong.c b/py/objint_longlong.c
index dbfb39809..b798c91cd 100644
--- a/py/objint_longlong.c
+++ b/py/objint_longlong.c
@@ -273,7 +273,7 @@ mp_obj_t mp_obj_new_int_from_float(mp_float_t val) {
 }
 #endif
 
-mp_obj_t mp_obj_new_int_from_str_len(const char **str, mp_uint_t len, bool neg, mp_uint_t base) {
+mp_obj_t mp_obj_new_int_from_str_len(const char **str, size_t len, bool neg, unsigned int base) {
     // TODO this does not honor the given length of the string, but it all cases it should anyway be null terminated
     // TODO check overflow
     mp_obj_int_t *o = m_new_obj(mp_obj_int_t);
diff --git a/py/objint_mpz.c b/py/objint_mpz.c
index 2b27df4f6..2cdf22505 100644
--- a/py/objint_mpz.c
+++ b/py/objint_mpz.c
@@ -407,9 +407,9 @@ mp_obj_t mp_obj_new_int_from_float(mp_float_t val) {
 }
 #endif
 
-mp_obj_t mp_obj_new_int_from_str_len(const char **str, mp_uint_t len, bool neg, mp_uint_t base) {
+mp_obj_t mp_obj_new_int_from_str_len(const char **str, size_t len, bool neg, unsigned int base) {
     mp_obj_int_t *o = mp_obj_int_new_mpz();
-    mp_uint_t n = mpz_set_from_str(&o->mpz, *str, len, neg, base);
+    size_t n = mpz_set_from_str(&o->mpz, *str, len, neg, base);
     *str += n;
     return MP_OBJ_FROM_PTR(o);
 }