diff --git a/ChangeLog b/ChangeLog
index ed5f50f2fe..d9f907c4d1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Nov 16 15:42:36 2015  Akinori MUSHA  <knu@iDaemons.org>
+
+	* lib/set.rb (#>=, #>, #<=, #<): Make use of Hash#>=, #>, #<, and
+	  #<= when comparing against an instance of the same kind.
+
 Mon Nov 16 15:33:11 2015  SHIBATA Hiroshi  <hsbt@ruby-lang.org>
 
 	* tool/rbinstall.rb: fix wrong permission for gem specification without
diff --git a/lib/set.rb b/lib/set.rb
index d612fdcb92..17775b07ea 100644
--- a/lib/set.rb
+++ b/lib/set.rb
@@ -220,33 +220,53 @@ class Set
 
   # Returns true if the set is a superset of the given set.
   def superset?(set)
-    set.is_a?(Set) or raise ArgumentError, "value must be a set"
-    return false if size < set.size
-    set.all? { |o| include?(o) }
+    case
+    when set.instance_of?(self.class)
+      @hash >= set.instance_variable_get(:@hash)
+    when set.is_a?(Set)
+      size >= set.size && set.all? { |o| include?(o) }
+    else
+      raise ArgumentError, "value must be a set"
+    end
   end
   alias >= superset?
 
   # Returns true if the set is a proper superset of the given set.
   def proper_superset?(set)
-    set.is_a?(Set) or raise ArgumentError, "value must be a set"
-    return false if size <= set.size
-    set.all? { |o| include?(o) }
+    case
+    when set.instance_of?(self.class)
+      @hash > set.instance_variable_get(:@hash)
+    when set.is_a?(Set)
+      size > set.size && set.all? { |o| include?(o) }
+    else
+      raise ArgumentError, "value must be a set"
+    end
   end
   alias > proper_superset?
 
   # Returns true if the set is a subset of the given set.
   def subset?(set)
-    set.is_a?(Set) or raise ArgumentError, "value must be a set"
-    return false if set.size < size
-    all? { |o| set.include?(o) }
+    case
+    when set.instance_of?(self.class)
+      @hash <= set.instance_variable_get(:@hash)
+    when set.is_a?(Set)
+      size <= set.size && all? { |o| set.include?(o) }
+    else
+      raise ArgumentError, "value must be a set"
+    end
   end
   alias <= subset?
 
   # Returns true if the set is a proper subset of the given set.
   def proper_subset?(set)
-    set.is_a?(Set) or raise ArgumentError, "value must be a set"
-    return false if set.size <= size
-    all? { |o| set.include?(o) }
+    case
+    when set.instance_of?(self.class)
+      @hash < set.instance_variable_get(:@hash)
+    when set.is_a?(Set)
+      size < set.size && all? { |o| set.include?(o) }
+    else
+      raise ArgumentError, "value must be a set"
+    end
   end
   alias < proper_subset?
 
diff --git a/test/test_set.rb b/test/test_set.rb
index 854bcc637b..66944f576f 100644
--- a/test/test_set.rb
+++ b/test/test_set.rb
@@ -2,6 +2,9 @@ require 'test/unit'
 require 'set'
 
 class TC_Set < Test::Unit::TestCase
+  class Set2 < Set
+  end
+
   def test_aref
     assert_nothing_raised {
       Set[]
@@ -211,16 +214,18 @@ class TC_Set < Test::Unit::TestCase
       set.superset?([2])
     }
 
-    assert_equal(true, set.superset?(Set[]))
-    assert_equal(true, set.superset?(Set[1,2]))
-    assert_equal(true, set.superset?(Set[1,2,3]))
-    assert_equal(false, set.superset?(Set[1,2,3,4]))
-    assert_equal(false, set.superset?(Set[1,4]))
+    [Set, Set2].each { |klass|
+      assert_equal(true, set.superset?(klass[]), klass.name)
+      assert_equal(true, set.superset?(klass[1,2]), klass.name)
+      assert_equal(true, set.superset?(klass[1,2,3]), klass.name)
+      assert_equal(false, set.superset?(klass[1,2,3,4]), klass.name)
+      assert_equal(false, set.superset?(klass[1,4]), klass.name)
 
-    assert_equal(true, set >= Set[1,2,3])
-    assert_equal(true, set >= Set[1,2])
+      assert_equal(true, set >= klass[1,2,3], klass.name)
+      assert_equal(true, set >= klass[1,2], klass.name)
 
-    assert_equal(true, Set[].superset?(Set[]))
+      assert_equal(true, Set[].superset?(klass[]), klass.name)
+    }
   end
 
   def test_proper_superset?
@@ -238,16 +243,18 @@ class TC_Set < Test::Unit::TestCase
       set.proper_superset?([2])
     }
 
-    assert_equal(true, set.proper_superset?(Set[]))
-    assert_equal(true, set.proper_superset?(Set[1,2]))
-    assert_equal(false, set.proper_superset?(Set[1,2,3]))
-    assert_equal(false, set.proper_superset?(Set[1,2,3,4]))
-    assert_equal(false, set.proper_superset?(Set[1,4]))
+    [Set, Set2].each { |klass|
+      assert_equal(true, set.proper_superset?(klass[]), klass.name)
+      assert_equal(true, set.proper_superset?(klass[1,2]), klass.name)
+      assert_equal(false, set.proper_superset?(klass[1,2,3]), klass.name)
+      assert_equal(false, set.proper_superset?(klass[1,2,3,4]), klass.name)
+      assert_equal(false, set.proper_superset?(klass[1,4]), klass.name)
 
-    assert_equal(false, set > Set[1,2,3])
-    assert_equal(true, set > Set[1,2])
+      assert_equal(false, set > klass[1,2,3], klass.name)
+      assert_equal(true, set > klass[1,2], klass.name)
 
-    assert_equal(false, Set[].proper_superset?(Set[]))
+      assert_equal(false, Set[].proper_superset?(klass[]), klass.name)
+    }
   end
 
   def test_subset?
@@ -265,16 +272,18 @@ class TC_Set < Test::Unit::TestCase
       set.subset?([2])
     }
 
-    assert_equal(true, set.subset?(Set[1,2,3,4]))
-    assert_equal(true, set.subset?(Set[1,2,3]))
-    assert_equal(false, set.subset?(Set[1,2]))
-    assert_equal(false, set.subset?(Set[]))
+    [Set, Set2].each { |klass|
+      assert_equal(true, set.subset?(klass[1,2,3,4]), klass.name)
+      assert_equal(true, set.subset?(klass[1,2,3]), klass.name)
+      assert_equal(false, set.subset?(klass[1,2]), klass.name)
+      assert_equal(false, set.subset?(klass[]), klass.name)
 
-    assert_equal(true, set <= Set[1,2,3])
-    assert_equal(true, set <= Set[1,2,3,4])
+      assert_equal(true, set <= klass[1,2,3], klass.name)
+      assert_equal(true, set <= klass[1,2,3,4], klass.name)
 
-    assert_equal(true, Set[].subset?(Set[1]))
-    assert_equal(true, Set[].subset?(Set[]))
+      assert_equal(true, Set[].subset?(klass[1]), klass.name)
+      assert_equal(true, Set[].subset?(klass[]), klass.name)
+    }
   end
 
   def test_proper_subset?
@@ -292,15 +301,17 @@ class TC_Set < Test::Unit::TestCase
       set.proper_subset?([2])
     }
 
-    assert_equal(true, set.proper_subset?(Set[1,2,3,4]))
-    assert_equal(false, set.proper_subset?(Set[1,2,3]))
-    assert_equal(false, set.proper_subset?(Set[1,2]))
-    assert_equal(false, set.proper_subset?(Set[]))
+    [Set, Set2].each { |klass|
+      assert_equal(true, set.proper_subset?(klass[1,2,3,4]), klass.name)
+      assert_equal(false, set.proper_subset?(klass[1,2,3]), klass.name)
+      assert_equal(false, set.proper_subset?(klass[1,2]), klass.name)
+      assert_equal(false, set.proper_subset?(klass[]), klass.name)
 
-    assert_equal(false, set < Set[1,2,3])
-    assert_equal(true, set < Set[1,2,3,4])
+      assert_equal(false, set < klass[1,2,3], klass.name)
+      assert_equal(true, set < klass[1,2,3,4], klass.name)
 
-    assert_equal(false, Set[].proper_subset?(Set[]))
+      assert_equal(false, Set[].proper_subset?(klass[]), klass.name)
+    }
   end
 
   def assert_intersect(expected, set, other)