diff --git a/py/objtuple.c b/py/objtuple.c
index c547da9..1935a67 100644
--- a/py/objtuple.c
+++ b/py/objtuple.c
@@ -32,7 +32,7 @@
 #include "py/runtime0.h"
 #include "py/runtime.h"
 
-STATIC mp_obj_t mp_obj_new_tuple_iterator(mp_obj_tuple_t *tuple, mp_uint_t cur);
+STATIC mp_obj_t mp_obj_new_tuple_iterator(mp_obj_tuple_t *tuple, size_t cur);
 
 /******************************************************************************/
 /* tuple                                                                      */
@@ -45,7 +45,7 @@
         mp_print_str(print, "(");
         kind = PRINT_REPR;
     }
-    for (mp_uint_t i = 0; i < o->len; i++) {
+    for (size_t i = 0; i < o->len; i++) {
         if (i > 0) {
             mp_print_str(print, ", ");
         }
@@ -80,8 +80,8 @@
 
             // TODO optimise for cases where we know the length of the iterator
 
-            mp_uint_t alloc = 4;
-            mp_uint_t len = 0;
+            size_t alloc = 4;
+            size_t len = 0;
             mp_obj_t *items = m_new(mp_obj_t, alloc);
 
             mp_obj_t iterable = mp_getiter(args[0]);
@@ -127,7 +127,7 @@
         case MP_UNARY_OP_HASH: {
             // start hash with pointer to empty tuple, to make it fairly unique
             mp_int_t hash = (mp_int_t)mp_const_empty_tuple;
-            for (mp_uint_t i = 0; i < self->len; i++) {
+            for (size_t i = 0; i < self->len; i++) {
                 hash += MP_OBJ_SMALL_INT_VALUE(mp_unary_op(MP_UNARY_OP_HASH, self->items[i]));
             }
             return MP_OBJ_NEW_SMALL_INT(hash);
@@ -235,7 +235,7 @@
 // the zero-length tuple
 const mp_obj_tuple_t mp_const_empty_tuple_obj = {{&mp_type_tuple}, 0};
 
-mp_obj_t mp_obj_new_tuple(mp_uint_t n, const mp_obj_t *items) {
+mp_obj_t mp_obj_new_tuple(size_t n, const mp_obj_t *items) {
     if (n == 0) {
         return mp_const_empty_tuple;
     }
@@ -243,7 +243,7 @@
     o->base.type = &mp_type_tuple;
     o->len = n;
     if (items) {
-        for (mp_uint_t i = 0; i < n; i++) {
+        for (size_t i = 0; i < n; i++) {
             o->items[i] = items[i];
         }
     }
@@ -270,7 +270,7 @@
     mp_obj_base_t base;
     mp_fun_1_t iternext;
     mp_obj_tuple_t *tuple;
-    mp_uint_t cur;
+    size_t cur;
 } mp_obj_tuple_it_t;
 
 STATIC mp_obj_t tuple_it_iternext(mp_obj_t self_in) {
@@ -284,7 +284,7 @@
     }
 }
 
-STATIC mp_obj_t mp_obj_new_tuple_iterator(mp_obj_tuple_t *tuple, mp_uint_t cur) {
+STATIC mp_obj_t mp_obj_new_tuple_iterator(mp_obj_tuple_t *tuple, size_t cur) {
     mp_obj_tuple_it_t *o = m_new_obj(mp_obj_tuple_it_t);
     o->base.type = &mp_type_polymorph_iter;
     o->iternext = tuple_it_iternext;