diff --git a/py/obj.c b/py/obj.c
index baac1f568..65b447494 100644
--- a/py/obj.c
+++ b/py/obj.c
@@ -86,7 +86,7 @@ void mp_obj_print(mp_obj_t o_in, mp_print_kind_t kind) {
 // helper function to print an exception with traceback
 void mp_obj_print_exception(const mp_print_t *print, mp_obj_t exc) {
     if (mp_obj_is_exception_instance(exc)) {
-        mp_uint_t n, *values;
+        size_t n, *values;
         mp_obj_exception_get_traceback(exc, &n, &values);
         if (n > 0) {
             assert(n % 3 == 0);
diff --git a/py/obj.h b/py/obj.h
index 88cef644f..3d9c00c52 100644
--- a/py/obj.h
+++ b/py/obj.h
@@ -680,8 +680,8 @@ 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);
 void mp_obj_exception_clear_traceback(mp_obj_t self_in);
-void mp_obj_exception_add_traceback(mp_obj_t self_in, qstr file, mp_uint_t line, qstr block);
-void mp_obj_exception_get_traceback(mp_obj_t self_in, mp_uint_t *n, mp_uint_t **values);
+void mp_obj_exception_add_traceback(mp_obj_t self_in, qstr file, size_t line, qstr block);
+void mp_obj_exception_get_traceback(mp_obj_t self_in, size_t *n, size_t **values);
 mp_obj_t mp_obj_exception_get_value(mp_obj_t self_in);
 mp_obj_t mp_obj_exception_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args);
 mp_obj_t mp_alloc_emergency_exception_buf(mp_obj_t size_in);
diff --git a/py/objexcept.c b/py/objexcept.c
index da31dddf7..ffe5ea041 100644
--- a/py/objexcept.c
+++ b/py/objexcept.c
@@ -346,9 +346,9 @@ mp_obj_t mp_obj_new_exception_msg_varg(const mp_obj_type_t *exc_type, const char
             offset += sizeof(void *) - 1;
             offset &= ~(sizeof(void *) - 1);
 
-            if ((mp_emergency_exception_buf_size - offset) > (sizeof(mp_uint_t) * 3)) {
+            if ((mp_emergency_exception_buf_size - offset) > (sizeof(o->traceback_data[0]) * 3)) {
                 // We have room to store some traceback.
-                o->traceback_data = (mp_uint_t*)((byte *)MP_STATE_VM(mp_emergency_exception_buf) + offset);
+                o->traceback_data = (size_t*)((byte *)MP_STATE_VM(mp_emergency_exception_buf) + offset);
                 o->traceback_alloc = (MP_STATE_VM(mp_emergency_exception_buf) + mp_emergency_exception_buf_size - (byte *)o->traceback_data) / sizeof(o->traceback_data[0]);
                 o->traceback_len = 0;
             }
@@ -429,14 +429,14 @@ void mp_obj_exception_clear_traceback(mp_obj_t self_in) {
     self->traceback_data = NULL;
 }
 
-void mp_obj_exception_add_traceback(mp_obj_t self_in, qstr file, mp_uint_t line, qstr block) {
+void mp_obj_exception_add_traceback(mp_obj_t self_in, qstr file, size_t line, qstr block) {
     GET_NATIVE_EXCEPTION(self, self_in);
 
     // append this traceback info to traceback data
     // if memory allocation fails (eg because gc is locked), just return
 
     if (self->traceback_data == NULL) {
-        self->traceback_data = m_new_maybe(mp_uint_t, 3);
+        self->traceback_data = m_new_maybe(size_t, 3);
         if (self->traceback_data == NULL) {
             return;
         }
@@ -444,7 +444,7 @@ void mp_obj_exception_add_traceback(mp_obj_t self_in, qstr file, mp_uint_t line,
         self->traceback_len = 0;
     } else if (self->traceback_len + 3 > self->traceback_alloc) {
         // be conservative with growing traceback data
-        mp_uint_t *tb_data = m_renew_maybe(mp_uint_t, self->traceback_data, self->traceback_alloc, self->traceback_alloc + 3, true);
+        size_t *tb_data = m_renew_maybe(size_t, self->traceback_data, self->traceback_alloc, self->traceback_alloc + 3, true);
         if (tb_data == NULL) {
             return;
         }
@@ -452,14 +452,14 @@ void mp_obj_exception_add_traceback(mp_obj_t self_in, qstr file, mp_uint_t line,
         self->traceback_alloc += 3;
     }
 
-    mp_uint_t *tb_data = &self->traceback_data[self->traceback_len];
+    size_t *tb_data = &self->traceback_data[self->traceback_len];
     self->traceback_len += 3;
-    tb_data[0] = (mp_uint_t)file;
-    tb_data[1] = (mp_uint_t)line;
-    tb_data[2] = (mp_uint_t)block;
+    tb_data[0] = file;
+    tb_data[1] = line;
+    tb_data[2] = block;
 }
 
-void mp_obj_exception_get_traceback(mp_obj_t self_in, mp_uint_t *n, mp_uint_t **values) {
+void mp_obj_exception_get_traceback(mp_obj_t self_in, size_t *n, size_t **values) {
     GET_NATIVE_EXCEPTION(self, self_in);
 
     if (self->traceback_data == NULL) {
diff --git a/py/objexcept.h b/py/objexcept.h
index 783f69466..88bce2b37 100644
--- a/py/objexcept.h
+++ b/py/objexcept.h
@@ -33,7 +33,7 @@ typedef struct _mp_obj_exception_t {
     mp_obj_base_t base;
     mp_uint_t traceback_alloc : (BITS_PER_WORD / 2);
     mp_uint_t traceback_len : (BITS_PER_WORD / 2);
-    mp_uint_t *traceback_data;
+    size_t *traceback_data;
     mp_obj_tuple_t *args;
 } mp_obj_exception_t;
 
diff --git a/py/vm.c b/py/vm.c
index 8c7c2265e..71e804c47 100644
--- a/py/vm.c
+++ b/py/vm.c
@@ -1311,9 +1311,9 @@ unwind_loop:
                 qstr block_name = mp_decode_uint(&ip);
                 qstr source_file = mp_decode_uint(&ip);
                 #endif
-                mp_uint_t bc = code_state->ip - code_state->code_info - code_info_size;
-                mp_uint_t source_line = 1;
-                mp_uint_t c;
+                size_t bc = code_state->ip - code_state->code_info - code_info_size;
+                size_t source_line = 1;
+                size_t c;
                 while ((c = *ip)) {
                     mp_uint_t b, l;
                     if ((c & 0x80) == 0) {