diff --git a/lib/protocol.js b/lib/protocol.js
index 56779d1..69891cb 100644
--- a/lib/protocol.js
+++ b/lib/protocol.js
@@ -164,10 +164,10 @@ var PrivateKey = {
 	},
 	decodeSize: function (buf, offset) {
 		var keyBuf = buf.slice(offset);
-		/* XXX: should find a way to make this faster */
-		var key = sshpk.PrivateKey.formats.
-		    rfc4253.readPartial('private', keyBuf);
-		return (key.toBuffer('rfc4253').length);
+		var ret = {};
+		sshpk.PrivateKey.formats.rfc4253.
+		    readInternal(ret, 'private', keyBuf);
+		return (ret.consumed);
 	},
 	decode: function (buf, offset) {
 		var size = PrivateKey.decodeSize(buf, offset);
diff --git a/package.json b/package.json
index ba44c76..d047d41 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "sshpk-agent",
-  "version": "1.2.0",
+  "version": "1.2.1",
   "description": "ssh-agent client for use with sshpk",
   "main": "lib/index.js",
   "scripts": {