diff --git a/ChangeLog b/ChangeLog
index 853d4071c2..3697bfc704 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Apr  4 11:33:57 2013  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* ext/openssl/ossl_bn.c (ossl_bn_to_i): Use bn2hex to speed up.
+	  In general, binary to/from decimal needs extra cost.
+
 Thu Apr  4 07:24:18 2013  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket/extconf.rb: Specify arguments to test functions.
diff --git a/ext/openssl/ossl_bn.c b/ext/openssl/ossl_bn.c
index 822b854efe..1038135ae8 100644
--- a/ext/openssl/ossl_bn.c
+++ b/ext/openssl/ossl_bn.c
@@ -226,10 +226,10 @@ ossl_bn_to_i(VALUE self)
 
     GetBN(self, bn);
 
-    if (!(txt = BN_bn2dec(bn))) {
+    if (!(txt = BN_bn2hex(bn))) {
 	ossl_raise(eBNError, NULL);
     }
-    num = rb_cstr_to_inum(txt, 10, Qtrue);
+    num = rb_cstr_to_inum(txt, 16, Qtrue);
     OPENSSL_free(txt);
 
     return num;