diff --git a/ChangeLog b/ChangeLog
index aff8606662e8e1..a28e7f134068e6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Jun 28 12:07:35 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* class.c (rb_define_class_id_under): raise TypeError exception
+	  same as ruby level class definition when superclass mismatch.
+
 Sun Jun 14 19:02:03 2015  Benoit Daloze  <eregontp@gmail.com>
 
 	* lib/net/ftp.rb (makeport): close the TCPServer
diff --git a/NEWS b/NEWS
index b516ee88f4a15a..b1e80ec7641f9c 100644
--- a/NEWS
+++ b/NEWS
@@ -143,6 +143,10 @@ with all sufficient information, see the ChangeLog file.
 
 === C API updates
 
+* rb_define_class_id_under() now raises a TypeError exception when the
+  class is already defined but its superclass does not match the given
+  superclass, as well as definitions in ruby level.
+
 === Build system updates
 
 === Implementation changes
diff --git a/class.c b/class.c
index f963f0c22a83f8..991172acbb6fa0 100644
--- a/class.c
+++ b/class.c
@@ -703,7 +703,8 @@ rb_define_class_id_under(VALUE outer, ID id, VALUE super)
 	    rb_raise(rb_eTypeError, "%"PRIsVALUE" is not a class", rb_id2str(id));
 	}
 	if (rb_class_real(RCLASS_SUPER(klass)) != super) {
-	    rb_name_error(id, "%"PRIsVALUE" is already defined", rb_id2str(id));
+	    rb_raise(rb_eTypeError, "superclass mismatch for class %"PRIsVALUE"",
+		     rb_id2str(id));
 	}
 	return klass;
     }
diff --git a/test/ruby/test_require.rb b/test/ruby/test_require.rb
index e7a903d6585936..7c2a5d3aa81b52 100644
--- a/test/ruby/test_require.rb
+++ b/test/ruby/test_require.rb
@@ -228,7 +228,7 @@ module Zlib; end
     assert_separately([], <<-INPUT)
       module Zlib; end
       class Zlib::Error; end
-      assert_raise(NameError) do
+      assert_raise(TypeError) do
         require 'zlib'
       end
     INPUT