diff --git a/ChangeLog b/ChangeLog
index 06aae7c313..09e6777efa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Mar 17 10:11:59 2014  Eric Wong  <e@80x24.org>
+
+	* variable.c (rb_const_set): delete existing entry on redefinition
+	  [Bug #9645]
+	* test/ruby/test_const.rb (test_redefinition): test for leak
+
 Sun Mar 16 21:33:01 2014  Zachary Scott  <e@zzak.io>
 
 	* lib/time.rb: [DOC] Fix timezone in example of Time.parse [Bug #9521]
diff --git a/test/ruby/test_const.rb b/test/ruby/test_const.rb
index dab45b7e08..c4a4d93249 100644
--- a/test/ruby/test_const.rb
+++ b/test/ruby/test_const.rb
@@ -1,5 +1,6 @@
 # -*- coding: us-ascii -*-
 require 'test/unit'
+require_relative 'envutil'
 
 class TestConst < Test::Unit::TestCase
   TEST1 = 1
@@ -54,5 +55,12 @@ class TestConst < Test::Unit::TestCase
 #{__FILE__}:#{__LINE__-1}: warning: already initialized constant #{c}::X
 #{__FILE__}:#{__LINE__-3}: warning: previous definition of X was here
 WARNING
+    code = <<-PRE
+olderr = $stderr.dup
+$stderr.reopen(File::NULL, "wb")
+350000.times { FOO = :BAR }
+$stderr.reopen(olderr)
+PRE
+    assert_no_memory_leak([], '', code, 'redefined constant')
   end
 end
diff --git a/variable.c b/variable.c
index c97c210af1..079f862797 100644
--- a/variable.c
+++ b/variable.c
@@ -2203,6 +2203,8 @@ rb_const_set(VALUE klass, ID id, VALUE val)
 		    rb_compile_warn(RSTRING_PTR(ce->file), ce->line,
 				    "previous definition of %"PRIsVALUE" was here", name);
 		}
+		st_delete(RCLASS_CONST_TBL(klass), &id, 0);
+		xfree(ce);
 	    }
 	}
     }