diff --git a/py/binary.c b/py/binary.c
index dfd25018c..83f28db91 100644
--- a/py/binary.c
+++ b/py/binary.c
@@ -42,7 +42,7 @@
 #define alignof(type) offsetof(struct { char c; type t; }, t)
 #endif
 
-size_t mp_binary_get_size(char struct_type, char val_type, mp_uint_t *palign) {
+size_t mp_binary_get_size(char struct_type, char val_type, size_t *palign) {
     size_t size = 0;
     int align = 1;
     switch (struct_type) {
@@ -113,7 +113,7 @@ size_t mp_binary_get_size(char struct_type, char val_type, mp_uint_t *palign) {
     return size;
 }
 
-mp_obj_t mp_binary_get_val_array(char typecode, void *p, mp_uint_t index) {
+mp_obj_t mp_binary_get_val_array(char typecode, void *p, size_t index) {
     mp_int_t val = 0;
     switch (typecode) {
         case 'b':
@@ -162,7 +162,7 @@ mp_obj_t mp_binary_get_val_array(char typecode, void *p, mp_uint_t index) {
 // The long long type is guaranteed to hold at least 64 bits, and size is at
 // most 8 (for q and Q), so we will always be able to parse the given data
 // and fit it into a long long.
-long long mp_binary_get_int(mp_uint_t size, bool is_signed, bool big_endian, const byte *src) {
+long long mp_binary_get_int(size_t size, bool is_signed, bool big_endian, const byte *src) {
     int delta;
     if (!big_endian) {
         delta = -1;
@@ -187,12 +187,12 @@ long long mp_binary_get_int(mp_uint_t size, bool is_signed, bool big_endian, con
 #define is_signed(typecode) (typecode > 'Z')
 mp_obj_t mp_binary_get_val(char struct_type, char val_type, byte *p_base, byte **ptr) {
     byte *p = *ptr;
-    mp_uint_t align;
+    size_t align;
 
     size_t size = mp_binary_get_size(struct_type, val_type, &align);
     if (struct_type == '@') {
         // Align p relative to p_base
-        p = p_base + (uintptr_t)MP_ALIGN(p - p_base, (size_t)align);
+        p = p_base + (uintptr_t)MP_ALIGN(p - p_base, align);
         #if MP_ENDIANNESS_LITTLE
         struct_type = '<';
         #else
@@ -231,7 +231,7 @@ mp_obj_t mp_binary_get_val(char struct_type, char val_type, byte *p_base, byte *
     }
 }
 
-void mp_binary_set_int(mp_uint_t val_sz, bool big_endian, byte *dest, mp_uint_t val) {
+void mp_binary_set_int(size_t val_sz, bool big_endian, byte *dest, mp_uint_t val) {
     if (MP_ENDIANNESS_LITTLE && !big_endian) {
         memcpy(dest, &val, val_sz);
     } else if (MP_ENDIANNESS_BIG && big_endian) {
@@ -252,12 +252,12 @@ void mp_binary_set_int(mp_uint_t val_sz, bool big_endian, byte *dest, mp_uint_t
 
 void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte *p_base, byte **ptr) {
     byte *p = *ptr;
-    mp_uint_t align;
+    size_t align;
 
     size_t size = mp_binary_get_size(struct_type, val_type, &align);
     if (struct_type == '@') {
         // Align p relative to p_base
-        p = p_base + (uintptr_t)MP_ALIGN(p - p_base, (size_t)align);
+        p = p_base + (uintptr_t)MP_ALIGN(p - p_base, align);
         if (MP_ENDIANNESS_LITTLE) {
             struct_type = '<';
         } else {
@@ -315,7 +315,7 @@ void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte *p
     mp_binary_set_int(MIN((size_t)size, sizeof(val)), struct_type == '>', p, val);
 }
 
-void mp_binary_set_val_array(char typecode, void *p, mp_uint_t index, mp_obj_t val_in) {
+void mp_binary_set_val_array(char typecode, void *p, size_t index, mp_obj_t val_in) {
     switch (typecode) {
 #if MICROPY_PY_BUILTINS_FLOAT
         case 'f':
@@ -342,7 +342,7 @@ void mp_binary_set_val_array(char typecode, void *p, mp_uint_t index, mp_obj_t v
     }
 }
 
-void mp_binary_set_val_array_from_int(char typecode, void *p, mp_uint_t index, mp_int_t val) {
+void mp_binary_set_val_array_from_int(char typecode, void *p, size_t index, mp_int_t val) {
     switch (typecode) {
         case 'b':
             ((signed char*)p)[index] = val;
diff --git a/py/binary.h b/py/binary.h
index ac24378d2..5c645bcaa 100644
--- a/py/binary.h
+++ b/py/binary.h
@@ -34,13 +34,13 @@
 // type-specification errors due to end-of-string.
 #define BYTEARRAY_TYPECODE 1
 
-size_t mp_binary_get_size(char struct_type, char val_type, mp_uint_t *palign);
-mp_obj_t mp_binary_get_val_array(char typecode, void *p, mp_uint_t index);
-void mp_binary_set_val_array(char typecode, void *p, mp_uint_t index, mp_obj_t val_in);
-void mp_binary_set_val_array_from_int(char typecode, void *p, mp_uint_t index, mp_int_t val);
+size_t mp_binary_get_size(char struct_type, char val_type, size_t *palign);
+mp_obj_t mp_binary_get_val_array(char typecode, void *p, size_t index);
+void mp_binary_set_val_array(char typecode, void *p, size_t index, mp_obj_t val_in);
+void mp_binary_set_val_array_from_int(char typecode, void *p, size_t index, mp_int_t val);
 mp_obj_t mp_binary_get_val(char struct_type, char val_type, byte *p_base, byte **ptr);
 void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte *p_base, byte **ptr);
-long long mp_binary_get_int(mp_uint_t size, bool is_signed, bool big_endian, const byte *src);
-void mp_binary_set_int(mp_uint_t val_sz, bool big_endian, byte *dest, mp_uint_t val);
+long long mp_binary_get_int(size_t size, bool is_signed, bool big_endian, const byte *src);
+void mp_binary_set_int(size_t val_sz, bool big_endian, byte *dest, mp_uint_t val);
 
 #endif // MICROPY_INCLUDED_PY_BINARY_H
diff --git a/py/modstruct.c b/py/modstruct.c
index 3e7d90ec1..36af4260e 100644
--- a/py/modstruct.c
+++ b/py/modstruct.c
@@ -97,7 +97,7 @@ STATIC size_t calc_size_items(const char *fmt, size_t *total_sz) {
             size += cnt;
         } else {
             total_cnt += cnt;
-            mp_uint_t align;
+            size_t align;
             size_t sz = mp_binary_get_size(fmt_type, *fmt, &align);
             while (cnt--) {
                 // Apply alignment