> diff -u XS.xs_orig XS.xs
--- XS.xs_orig  2017-09-05 13:30:07.933454000 +0300
+++ XS.xs       2017-09-06 08:35:35.224749000 +0300
@@ -1214,7 +1214,7 @@
       SvPOK_only (sv);
       *SvEND (sv) = 0;
 
-      if (utf8)
+      if (utf8 && !(dec->json.flags & F_LATIN1))
         SvUTF8_on (sv);
     }
   else