diff --git a/youtube_dl/socks.py b/youtube_dl/socks.py
index 63d19b3a5..fece28062 100644
--- a/youtube_dl/socks.py
+++ b/youtube_dl/socks.py
@@ -60,7 +60,7 @@ class ProxyError(IOError):
 
     def __init__(self, code=None, msg=None):
         if code is not None and msg is None:
-            msg = self.CODES.get(code) and 'unknown error'
+            msg = self.CODES.get(code) or 'unknown error'
         super(ProxyError, self).__init__(code, msg)