diff --git a/ChangeLog b/ChangeLog
index 5fca22bc5a..92cca25a4d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Tue Jan  7 04:35:46 2014  Aman Gupta <ruby@tmm1.net>
+
+	* array.c (ary_add_hash): Fix consistency issue between Array#uniq and
+	  Array#uniq! [Bug #9340] [ruby-core:59457]
+	* test/ruby/test_array.rb (class TestArray): regression test for above.
+
 Mon Jan  6 21:28:48 2014  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
 
 	* .gitignore: ignore *-fake.rb generated even when CROSS_COMPILING = no
diff --git a/array.c b/array.c
index c4869789e5..775fb243bd 100644
--- a/array.c
+++ b/array.c
@@ -3908,7 +3908,9 @@ ary_add_hash(VALUE hash, VALUE ary)
 
     for (i=0; i<RARRAY_LEN(ary); i++) {
 	VALUE elt = RARRAY_AREF(ary, i);
-	rb_hash_aset(hash, elt, elt);
+	if (rb_hash_lookup2(hash, elt, Qundef) == Qundef) {
+	    rb_hash_aset(hash, elt, elt);
+	}
     }
     return hash;
 }
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index b648c404ed..6ff304acb2 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -1524,6 +1524,11 @@ class TestArray < Test::Unit::TestCase
     assert(a.none?(&:frozen?))
     assert_equal(%w(a), b)
     assert(b.none?(&:frozen?))
+
+    bug9340 = "[ruby-core:59457]"
+    ary = [bug9340, bug9340.dup, bug9340.dup]
+    assert_equal 1, ary.uniq.size
+    assert_same bug9340, ary.uniq[0]
   end
 
   def test_uniq_with_block