diff --git a/ChangeLog b/ChangeLog
index 58ce5c9705..4eb6eccce1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Tue Oct 16 19:48:01 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* re.c (rb_reg_s_union): check for encoding of original object.
+
 Tue Oct 16 18:28:51 2007  Tanaka Akira  <akr@fsij.org>
 
 	* debug.c: use enum for constants for gdb if possible.
diff --git a/re.c b/re.c
index 37e46989e8..b117cb4651 100644
--- a/re.c
+++ b/re.c
@@ -1776,15 +1776,17 @@ rb_reg_s_union(VALUE self, VALUE args0)
 
 	for (i = 0; i < argc; i++) {
 	    volatile VALUE v;
+	    VALUE e = rb_ary_entry(args0, i);
 	    if (0 < i)
 		rb_str_buf_cat2(source, "|");
-	    v = rb_check_regexp_type(rb_ary_entry(args0, i));
-	    rb_enc_check(tmp, v);
+	    v = rb_check_regexp_type(e);
 	    if (!NIL_P(v)) {
+		rb_enc_check(tmp, v);
 		v = rb_reg_to_s(v);
 	    }
 	    else {
-		v = rb_reg_s_quote(Qnil, rb_ary_entry(args0, i));
+		rb_enc_check(tmp, e);
+		v = rb_reg_s_quote(Qnil, e);
 	    }
 	    rb_str_buf_append(source, v);
 	}