re.c: stop a wrong warning of "flags ignored" on Regexp.new(//)

[Bug #18669]

1 files changed, 1 insertions, 1 deletions

diff --git a/re.c b/re.c
index 8666e449ec..a4cd2e39b9 100644
--- a/re.c
+++ b/re.c
@@ -3557,7 +3557,7 @@ rb_reg_initialize_m(int argc, VALUE *argv, VALUE self)
     if (RB_TYPE_P(src, T_REGEXP)) {
 	VALUE re = src;
 
-	if (opts != Qundef) {
+	if (opts != Qnil) {
 	    rb_warn("flags ignored");
 	}
 	rb_reg_check(re);