1 files changed, 1 insertions, 1 deletions
diff --git a/string.c b/string.c
index 49e3c18152..2fb67efe92 100644
--- a/string.c
+++ b/string.c
@@ -4158,7 +4158,7 @@ rb_str_sub_bang(int argc, VALUE *argv, VALUE str)
 	memcpy(p + beg0, rp, rlen);
 	len += rlen - plen;
 	STR_SET_LEN(str, len);
-	RSTRING_PTR(str)[len] = '\0';
+	TERM_FILL(&RSTRING_PTR(str)[len], TERM_LEN(str));
 	ENC_CODERANGE_SET(str, cr);
 	if (tainted) OBJ_TAINT(str);