diff --git a/pyrad/tests/testPacket.py b/pyrad/tests/testPacket.py
index 08c21be..43c110f 100644
--- a/pyrad/tests/testPacket.py
+++ b/pyrad/tests/testPacket.py
@@ -465,12 +465,8 @@ def setUp(self):
     def testVerifyChapPasswd(self):
         chap_id = b'9'
         chap_challenge = b'987654321'
-        chap_password = b'%s%s' % (chap_id, md5_constructor(
-            b'%s%s%s' % (
-                chap_id,
-                b'test_password',
-                chap_challenge
-            )).digest())
+        chap_password = chap_id + md5_constructor(
+                chap_id + b'test_password' + chap_challenge).digest()
         pkt = self.client.CreateAuthPacket(
             code=packet.AccessChallenge,
             authenticator=b'ABCDEFG',
diff --git a/pyrad/tools.py b/pyrad/tools.py
index 9b330b1..8d2b37f 100644
--- a/pyrad/tools.py
+++ b/pyrad/tools.py
@@ -110,11 +110,10 @@ def EncodeAscendBinary(str):
             terms[key] = struct.pack('B', int(value))
 
     trailer = 8 * b'\x00'
-    result = b'%s%s%s\x00%s%s%s%s%s\x00%s%s%s%s\x00\x00%s' % (
+    result = b'%s%s%s\x00%s%s%s%s%s\x00%s%s%s%s\x00\x00' % (
         terms['family'], terms['action'], terms['direction'], terms['src'],
         terms['dst'], terms['srcl'], terms['dstl'], terms['proto'],
-        terms['sport'], terms['dport'], terms['sportq'], terms['dportq'],
-        trailer)
+        terms['sport'], terms['dport'], terms['sportq'], terms['dportq']) + trailer
     return result