--- a/Size.xs	2013-05-10 12:35:23.000000000 +0000
+++ b/Size.xs	2013-08-27 14:52:53.000000000 +0000
@@ -707,7 +707,7 @@
   }
   st->total_size += sizeof(SV) + body_sizes[type];
 
-  if (type >= SVt_PVMG) {
+  if (SvMAGICAL(thing)) {
       magic_size(aTHX_ thing, st);
   }