diff --git a/ChangeLog b/ChangeLog
index d1e7d0f0e2..b037b27a64 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Mon Oct  4 09:30:42 2010  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* ext/openssl/lib/openssl/bn.rb (Integer#to_bn): OpenSSL::BN.new
+	  accepts only Strings, so call Integer#to_s(16).
+	  16 is for an optimization. [ruby-dev:42336]
+
 Mon Oct  4 07:57:51 2010  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* cont.c (fiber_memsize): Return size.
diff --git a/ext/openssl/lib/openssl/bn.rb b/ext/openssl/lib/openssl/bn.rb
index e7cbf2cfaf..624c13715c 100644
--- a/ext/openssl/lib/openssl/bn.rb
+++ b/ext/openssl/lib/openssl/bn.rb
@@ -29,7 +29,7 @@ end # OpenSSL
 #
 class Integer
   def to_bn
-    OpenSSL::BN::new(self)
+    OpenSSL::BN::new(self.to_s(16), 16)
   end
 end # Integer
 
diff --git a/test/openssl/test_bn.rb b/test/openssl/test_bn.rb
index da77a556b0..d913d0c953 100644
--- a/test/openssl/test_bn.rb
+++ b/test/openssl/test_bn.rb
@@ -8,6 +8,11 @@ require "test/unit"
 if defined?(OpenSSL)
 
 class OpenSSL::TestBN < Test::Unit::TestCase
+  def test_integer_to_bn
+    assert_equal(999.to_bn, OpenSSL::BN.new(999.to_s(16), 16))
+    assert_equal((2 ** 107 - 1).to_bn, OpenSSL::BN.new((2 ** 107 - 1).to_s(16), 16))
+  end
+
   def test_prime_p
     OpenSSL::BN.new((2 ** 107 - 1).to_s(16), 16).prime?
     OpenSSL::BN.new((2 ** 127 - 1).to_s(16), 16).prime?(1)