Accept both lower and camelcase userip.
diff --git a/apiclient/discovery.py b/apiclient/discovery.py
index b99f7c2..825604a 100644
--- a/apiclient/discovery.py
+++ b/apiclient/discovery.py
@@ -49,7 +49,7 @@
 
 # Query parameters that work, but don't appear in discovery
 STACK_QUERY_PARAMETERS = ['trace', 'fields', 'pp', 'prettyPrint', 'userIp',
-  'strict']
+  'userip', 'strict']
 
 
 def key2param(key):