Index: ext/bigdecimal/bigdecimal.c
===================================================================
--- ext/bigdecimal/bigdecimal.c	(revision 49401)
+++ ext/bigdecimal/bigdecimal.c	(working copy)
@@ -124,8 +124,9 @@
      * 1.0.0: Ruby 1.8.0
      * 1.0.1: Ruby 1.8.1
      * 1.1.0: Ruby 1.9.3
+     * 1.2.0: Ruby 2.3.0
     */
-    return rb_str_new2("1.1.0");
+    return rb_str_new2("1.2.0");
 }
 
 /*
@@ -3259,6 +3260,15 @@
     arg = rb_str_new2("NaN");
     /* 'Not a Number' value. */
     rb_define_const(rb_cBigDecimal, "NAN", BigDecimal_global_new(1, &arg, rb_cBigDecimal));
+    arg = rb_str_new2("0");
+    /* Singleton instance of BigDecimal.new('0'). */
+    rb_define_const(rb_cBigDecimal, "ZERO", BigDecimal_global_new(1, &arg, rb_cBigDecimal));
+    arg = rb_str_new2("1");
+    /* Singleton instance of BigDecimal.new('1'). */
+    rb_define_const(rb_cBigDecimal, "ONE", BigDecimal_global_new(1, &arg, rb_cBigDecimal));
+    arg = rb_str_new2("10");
+    /* Singleton instance of BigDecimal.new('10'). */
+    rb_define_const(rb_cBigDecimal, "TEN", BigDecimal_global_new(1, &arg, rb_cBigDecimal));
 
 
     /* instance methods */
Index: ext/bigdecimal/bigdecimal.h
===================================================================
--- ext/bigdecimal/bigdecimal.h	(revision 49401)
+++ ext/bigdecimal/bigdecimal.h	(working copy)
@@ -114,6 +114,7 @@
 #define SZ_PINF "+Infinity"
 #define SZ_NINF "-Infinity"
 
+
 /*
  *   #define VP_EXPORT other than static to let VP_ routines
  *   be called from outside of this module.
Index: test/bigdecimal/test_bigdecimal.rb
===================================================================
--- test/bigdecimal/test_bigdecimal.rb	(revision 49401)
+++ test/bigdecimal/test_bigdecimal.rb	(working copy)
@@ -1552,4 +1552,25 @@
     Thread.current.keys.to_s
     EOS
   end
+
+  def test_zero_const
+    assert_equal(BigDecimal::ZERO, BigDecimal.new('0'))
+    assert_equal(BigDecimal::ZERO.object_id, BigDecimal::ZERO.object_id)
+    assert_equal((-BigDecimal::ZERO), BigDecimal.new('-0'))
+    assert_equal((-BigDecimal::ZERO).object_id, (-BigDecimal::ZERO).object_id)
+  end
+
+  def test_one_const
+    assert_equal(BigDecimal::ONE, BigDecimal.new('1'))
+    assert_equal(BigDecimal::ONE.object_id, BigDecimal::ONE.object_id)
+    assert_equal((-BigDecimal::ONE), BigDecimal.new('-1'))
+    assert_equal((-BigDecimal::ONE).object_id, (-BigDecimal::ONE).object_id)
+  end
+
+  def test_ten_const
+    assert_equal(BigDecimal::TEN, BigDecimal.new('10'))
+    assert_equal(BigDecimal::TEN.object_id, BigDecimal::TEN.object_id)
+    assert_equal((-BigDecimal::TEN), BigDecimal.new('-10'))
+    assert_equal((-BigDecimal::TEN).object_id, (-BigDecimal::TEN).object_id)
+  end
 end