diff --git a/py/modmicropython.c b/py/modmicropython.c
index 9c578a89c9..b5ab2e2653 100644
--- a/py/modmicropython.c
+++ b/py/modmicropython.c
@@ -79,9 +79,9 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(mp_micropython_mem_info_obj, 0, 1, mp
 
 STATIC mp_obj_t mp_micropython_qstr_info(mp_uint_t n_args, const mp_obj_t *args) {
     (void)args;
-    mp_uint_t n_pool, n_qstr, n_str_data_bytes, n_total_bytes;
+    size_t n_pool, n_qstr, n_str_data_bytes, n_total_bytes;
     qstr_pool_info(&n_pool, &n_qstr, &n_str_data_bytes, &n_total_bytes);
-    mp_printf(&mp_plat_print, "qstr pool: n_pool=" UINT_FMT ", n_qstr=" UINT_FMT ", n_str_data_bytes=" UINT_FMT ", n_total_bytes=" UINT_FMT "\n",
+    mp_printf(&mp_plat_print, "qstr pool: n_pool=%u, n_qstr=%u, n_str_data_bytes=%u, n_total_bytes=%u\n",
         n_pool, n_qstr, n_str_data_bytes, n_total_bytes);
     if (n_args == 1) {
         // arg given means dump qstr data
diff --git a/py/mpstate.h b/py/mpstate.h
index c7604e03af..012b0ef189 100644
--- a/py/mpstate.h
+++ b/py/mpstate.h
@@ -138,8 +138,8 @@ typedef struct _mp_state_vm_t {
     // pointer and sizes to store interned string data
     // (qstr_last_chunk can be root pointer but is also stored in qstr pool)
     byte *qstr_last_chunk;
-    mp_uint_t qstr_last_alloc;
-    mp_uint_t qstr_last_used;
+    size_t qstr_last_alloc;
+    size_t qstr_last_used;
 
     // Stack top at the start of program
     // Note: this entry is used to locate the end of the root pointer section.
diff --git a/py/qstr.c b/py/qstr.c
index 090be64ad1..4268946fbe 100644
--- a/py/qstr.c
+++ b/py/qstr.c
@@ -165,7 +165,7 @@ qstr qstr_from_strn(const char *str, size_t len) {
         // qstr does not exist in interned pool so need to add it
 
         // compute number of bytes needed to intern this string
-        mp_uint_t n_bytes = MICROPY_QSTR_BYTES_IN_HASH + MICROPY_QSTR_BYTES_IN_LEN + len + 1;
+        size_t n_bytes = MICROPY_QSTR_BYTES_IN_HASH + MICROPY_QSTR_BYTES_IN_LEN + len + 1;
 
         if (MP_STATE_VM(qstr_last_chunk) != NULL && MP_STATE_VM(qstr_last_used) + n_bytes > MP_STATE_VM(qstr_last_alloc)) {
             // not enough room at end of previously interned string so try to grow
@@ -221,7 +221,7 @@ byte *qstr_build_start(size_t len, byte **q_ptr) {
 qstr qstr_build_end(byte *q_ptr) {
     qstr q = qstr_find_strn((const char*)Q_GET_DATA(q_ptr), Q_GET_LENGTH(q_ptr));
     if (q == 0) {
-        mp_uint_t len = Q_GET_LENGTH(q_ptr);
+        size_t len = Q_GET_LENGTH(q_ptr);
         mp_uint_t hash = qstr_compute_hash(Q_GET_DATA(q_ptr), len);
         Q_SET_HASH(q_ptr, hash);
         q_ptr[MICROPY_QSTR_BYTES_IN_HASH + MICROPY_QSTR_BYTES_IN_LEN + len] = '\0';
@@ -253,7 +253,7 @@ const byte *qstr_data(qstr q, size_t *len) {
     return Q_GET_DATA(qd);
 }
 
-void qstr_pool_info(mp_uint_t *n_pool, mp_uint_t *n_qstr, mp_uint_t *n_str_data_bytes, mp_uint_t *n_total_bytes) {
+void qstr_pool_info(size_t *n_pool, size_t *n_qstr, size_t *n_str_data_bytes, size_t *n_total_bytes) {
     *n_pool = 0;
     *n_qstr = 0;
     *n_str_data_bytes = 0;
diff --git a/py/qstr.h b/py/qstr.h
index 333c60f80a..6f9da14acb 100644
--- a/py/qstr.h
+++ b/py/qstr.h
@@ -47,9 +47,9 @@ typedef mp_uint_t qstr;
 
 typedef struct _qstr_pool_t {
     struct _qstr_pool_t *prev;
-    mp_uint_t total_prev_len;
-    mp_uint_t alloc;
-    mp_uint_t len;
+    size_t total_prev_len;
+    size_t alloc;
+    size_t len;
     const byte *qstrs[];
 } qstr_pool_t;
 
@@ -71,7 +71,7 @@ const char *qstr_str(qstr q);
 size_t qstr_len(qstr q);
 const byte *qstr_data(qstr q, size_t *len);
 
-void qstr_pool_info(mp_uint_t *n_pool, mp_uint_t *n_qstr, mp_uint_t *n_str_data_bytes, mp_uint_t *n_total_bytes);
+void qstr_pool_info(size_t *n_pool, size_t *n_qstr, size_t *n_str_data_bytes, size_t *n_total_bytes);
 void qstr_dump_data(void);
 
 #endif // __MICROPY_INCLUDED_PY_QSTR_H__