diff --git a/ssh-audit.py b/ssh-audit.py
index f81f2d2..cdd9b8c 100755
--- a/ssh-audit.py
+++ b/ssh-audit.py
@@ -172,7 +172,8 @@ class ReadBuf(object):
 		n = self.read_int()
 		return self.read(n)
 	
-	def _parse_mpint(self, v, pad, sf):
+	@classmethod
+	def _parse_mpint(cls, v, pad, sf):
 		r = 0
 		if len(v) % 4:
 			v = pad * (4 - (len(v) % 4)) + v
@@ -225,27 +226,38 @@ class WriteBuf(object):
 	def write_list(self, v):
 		self.write_string(u','.join(v))
 	
-	def _create_mpint(self, v):
-		length = v.bit_length() // 8 + (1 if v != 0 else 0)
+	@classmethod
+	def _bitlength(cls, n):
+		try:
+			return n.bit_length()
+		except AttributeError:
+			return len(bin(n)) - (2 if n > 0 else 3)
+		
+	@classmethod
+	def _create_mpint(cls, n, bits=None):
+		if bits is None:
+			bits = cls._bitlength(n)
+		length = bits // 8 + (1 if n != 0 else 0)
 		ql = (length + 7) // 8
 		fmt, v2 = '>{0}Q'.format(ql), [b'\x00'] * ql
 		for i in range(ql):
-			v2[ql - i - 1] = (v & 0xffffffffffffffff)
-			v >>= 64
+			v2[ql - i - 1] = (n & 0xffffffffffffffff)
+			n >>= 64
 		data = bytes(struct.pack(fmt, *v2)[-length:])
 		if data.startswith(b'\xff\x80'):
 			data = data[1:]
 		return data
 	
-	def write_mpint1(self, v):
+	def write_mpint1(self, n):
 		# NOTE: Data Type Enc @ http://www.snailbook.com/docs/protocol-1.5.txt
-		data = self._create_mpint(v)
-		self.write(struct.pack('>H', v.bit_length()))
+		bits = self._bitlength(n)
+		data = self._create_mpint(n, bits)
+		self.write(struct.pack('>H', bits))
 		return self.write(data)
 	
-	def write_mpint2(self, v):
+	def write_mpint2(self, n):
 		# NOTE: Section 5 @ https://www.ietf.org/rfc/rfc4251.txt
-		data = self._create_mpint(v)
+		data = self._create_mpint(n)
 		return self.write_string(data)
 	
 	def write_flush(self):