diff --git a/ChangeLog b/ChangeLog
index 5bdc6cdc12..a62b4fe4b7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Jun 22 10:31:39 2006  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* string.c (rb_str_aref): "abc"[3] should not return an empty
+	  string but nil.  [ruby-dev:28786]
+
 Thu Jun 22 05:15:58 2006  Tanaka Akira  <akr@m17n.org>
 
 	* ext/socket/socket.c (sock_s_socketpair): try GC only once.
diff --git a/string.c b/string.c
index f254915f9b..136235580c 100644
--- a/string.c
+++ b/string.c
@@ -1478,6 +1478,12 @@ rb_str_aref(VALUE str, VALUE indx)
 	idx = FIX2LONG(indx);
 
       num_index:
+	if (idx < 0) {
+	    idx = RSTRING(str)->len + idx;
+	}
+	if (idx < 0 || RSTRING(str)->len <= idx) {
+	    return Qnil;
+	}
 	return rb_str_substr(str, idx, 1);
 
       case T_REGEXP: