--- perl-current/toke.c
+++ perl-current/toke.c
@@ -3561,7 +3561,7 @@
     default:
 	if (isIDFIRST_lazy_if(s,UTF))
 	    goto keylookup;
-	len = UTF ? Perl_utf8_length((U8 *) PL_linestart, (U8 *) s) : (STRLEN) (s - PL_linestart);
+	len = UTF ? Perl_utf8_length(aTHX_ (U8 *) PL_linestart, (U8 *) s) : (STRLEN) (s - PL_linestart);
 	Perl_croak(aTHX_ "Unrecognized character \\x%02X in column %d", *s & 255, (int) len + 1);
     case 4:
     case 26: