Change PyUnicode_KIND to 1,2,4. Drop _KIND_SIZE and _CHARACTER_SIZE.
diff --git a/Modules/_json.c b/Modules/_json.c
index 0f550c1..e49d1b2 100644
--- a/Modules/_json.c
+++ b/Modules/_json.c
@@ -365,7 +365,7 @@
             APPEND_OLD_CHUNK
                 chunk = PyUnicode_FromKindAndData(
                     kind,
-                    (char*)buf + PyUnicode_KIND_SIZE(kind, end),
+                    (char*)buf + kind * end,
                     next - end);
             if (chunk == NULL) {
                 goto bail;
@@ -931,7 +931,7 @@
     if (custom_func) {
         /* copy the section we determined to be a number */
         numstr = PyUnicode_FromKindAndData(kind,
-                                           (char*)str + PyUnicode_KIND_SIZE(kind, start),
+                                           (char*)str + kind * start,
                                            idx - start);
         if (numstr == NULL)
             return NULL;