diff --git a/ChangeLog b/ChangeLog
index 546871d0c3..8c9f72f91e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Jun 11 13:17:34 2015  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* test/test_cmath.rb (TestCMath#test_trigonometric_functions): should
+	  not compare float values (in complex values) by `==`.
+
 Thu Jun 11 08:52:01 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* method.h: embed rb_method_entry_t::attr::flags (5 bits) into
diff --git a/test/test_cmath.rb b/test/test_cmath.rb
index c48bb4d673..7d18b40565 100644
--- a/test/test_cmath.rb
+++ b/test/test_cmath.rb
@@ -23,13 +23,13 @@ class TestCMath < Test::Unit::TestCase
   end
 
   def test_trigonometric_functions
-    assert_equal CMath.sinh(2).i, CMath.sin(2i)
-    assert_equal CMath.cosh(2),   CMath.cos(2i)
-    assert_equal CMath.tanh(2).i, CMath.tan(2i)
+    assert_in_delta CMath.sinh(2).i, CMath.sin(2i)
+    assert_in_delta CMath.cosh(2),   CMath.cos(2i)
+    assert_in_delta CMath.tanh(2).i, CMath.tan(2i)
 
-    assert_equal CMath.sin(2).i, CMath.sinh(2i)
-    assert_equal CMath.cos(2),   CMath.cosh(2i)
-    assert_equal CMath.tan(2).i, CMath.tanh(2i)
+    assert_in_delta CMath.sin(2).i, CMath.sinh(2i)
+    assert_in_delta CMath.cos(2),   CMath.cosh(2i)
+    assert_in_delta CMath.tan(2).i, CMath.tanh(2i)
 
     assert_in_delta 1+1i, CMath.sin(CMath.asin(1+1i))
     assert_in_delta 1+1i, CMath.cos(CMath.acos(1+1i))