diff --git a/autobahn/wamp/auth.py b/autobahn/wamp/auth.py
index 79de17658..0120b0d99 100644
--- a/autobahn/wamp/auth.py
+++ b/autobahn/wamp/auth.py
@@ -158,7 +158,7 @@ def __init__(self, **kw):
                     "Must provide '{}' for cryptosign".format(key)
                 )
         for key in kw.get('authextra', dict()):
-            if key not in ['pubkey']:
+            if key not in ['pubkey', 'channel_binding']:
                 raise ValueError(
                     "Unexpected key '{}' in 'authextra'".format(key)
                 )