diff --git a/py/mpprint.c b/py/mpprint.c
index a569ef793..74912eb5f 100644
--- a/py/mpprint.c
+++ b/py/mpprint.c
@@ -512,7 +512,8 @@ int mp_vprintf(const mp_print_t *print, const char *fmt, va_list args) {
                 break;
             case 'p':
             case 'P': // don't bother to handle upcase for 'P'
-                chrs += mp_print_int(print, va_arg(args, unsigned int), 0, 16, 'a', flags, fill, width);
+                // Use unsigned long int to work on both ILP32 and LP64 systems
+                chrs += mp_print_int(print, va_arg(args, unsigned long int), 0, 16, 'a', flags, fill, width);
                 break;
 #if MICROPY_PY_BUILTINS_FLOAT
             case 'e':