diff --git a/ChangeLog b/ChangeLog
index 95ac72edb1..9288d7ca4e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat May  1 09:43:06 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/test/unit/assertions.rb (Test::Unit::Assertions#assert):
+	  filter out traces in minitest directory.  [ruby-core:29908]
+
 Sat May  1 06:42:57 2010  wanabe  <s.wanabe@gmail.com>
 
 	* win32/win32.c: add declaration of wstati64 for gcc.
diff --git a/lib/test/unit/assertions.rb b/lib/test/unit/assertions.rb
index 9a6d643623..234775f1a3 100644
--- a/lib/test/unit/assertions.rb
+++ b/lib/test/unit/assertions.rb
@@ -13,7 +13,7 @@ module Test
       def assert(test, msg = (nomsg = true; nil))
         unless nomsg or msg.instance_of?(String) or msg.instance_of?(Proc) or
             (bt = caller).shift.rindex(MiniTest::MINI_DIR, 0)
-          bt = MiniTest.filter_backtrace(bt)
+          bt = MiniTest.delete_if {|s| rindex(MiniTest::MINI_DIR, 0)}
           raise ArgumentError, "assertion message must be String or Proc, but #{msg.class} was given.", bt
         end
         super