diff --git a/aiosocks/protocols.py b/aiosocks/protocols.py
index 98b5515..541dda7 100644
--- a/aiosocks/protocols.py
+++ b/aiosocks/protocols.py
@@ -75,6 +75,9 @@ class Socks4Protocol(SocksProtocol):
 
         super().__init__(proxy, proxy_auth, dst, remote_resolve, loop)
 
+        if proxy_auth is None:
+            self._auth = Socks4Auth('')
+
     async def socks_request(self, cmd):
         # prepare destination addr/port
         host, port = self._dst_host, self._dst_port
@@ -119,6 +122,9 @@ class Socks5Protocol(SocksProtocol):
 
         super().__init__(proxy, proxy_auth, dst, remote_resolve, loop)
 
+        if proxy_auth is None:
+            self._auth = Socks5Auth('', '')
+
     async def socks_request(self, cmd):
         # send available auth methods
         if self._auth.login and self._auth.password: