diff --git a/pyVoIP/SIP.py b/pyVoIP/SIP.py
index 0c05c70..39a84a1 100644
--- a/pyVoIP/SIP.py
+++ b/pyVoIP/SIP.py
@@ -599,17 +599,19 @@ def genTag(self):
         return tag
   
   def genSIPVersionNotSupported(self, request):
-    regRequest = "SIP/2.0 505 SIP Version Not Supported\r\n"
-    regRequest += "Via: SIP/2.0/UDP "+request.headers['Via']['address'][0]+":"+request.headers['Via']['address'][1]+";branch="+request.headers['Via']['branch']+"\r\n"
-    regRequest += "From: "+request.headers['From']['raw']+";tag="+request.headers['From']['tag']+"\r\n"
-    regRequest += "To: "+request.headers['To']['raw']+";tag="+self.genTag()+"\r\n"
-    regRequest += "Call-ID: "+request.headers['Call-ID']+"\r\n"
-    regRequest += "CSeq: "+request.headers['CSeq']['check']+" "+request.headers['CSeq']['method']+"\r\n"
-    regRequest += "Contact: "+request.headers['Contact']+"\r\n" #TODO: Add Supported
-    regRequest += "User-Agent: pyVoIP """+pyVoIP.__version__+"\r\n"
-    regRequest += "Warning: 399 GS \"Unable to accept call\"\r\n"
-    regRequest += "Allow: "+(", ".join(pyVoIP.SIPCompatibleMethods))+"\r\n"
-    regRequest += "Content-Length: 0\r\n\r\n"
+    response = "SIP/2.0 505 SIP Version Not Supported\r\n"
+    response += "Via: SIP/2.0/UDP "+request.headers['Via']['address'][0]+":"+request.headers['Via']['address'][1]+";branch="+request.headers['Via']['branch']+"\r\n"
+    response += "From: "+request.headers['From']['raw']+";tag="+request.headers['From']['tag']+"\r\n"
+    response += "To: "+request.headers['To']['raw']+";tag="+self.genTag()+"\r\n"
+    response += "Call-ID: "+request.headers['Call-ID']+"\r\n"
+    response += "CSeq: "+request.headers['CSeq']['check']+" "+request.headers['CSeq']['method']+"\r\n"
+    response += "Contact: "+request.headers['Contact']+"\r\n" #TODO: Add Supported
+    response += "User-Agent: pyVoIP """+pyVoIP.__version__+"\r\n"
+    response += "Warning: 399 GS \"Unable to accept call\"\r\n"
+    response += "Allow: "+(", ".join(pyVoIP.SIPCompatibleMethods))+"\r\n"
+    response += "Content-Length: 0\r\n\r\n"
+
+    return response
   
   def genAuthorization(self, request):
     HA1 = hashlib.md5(self.username.encode('utf8')+b':'+request.authentication['realm'].encode('utf8')+b':'+self.password.encode('utf8')).hexdigest().encode('utf8')