Index: src/lxml/xpath.pxi
===================================================================
--- src/lxml/xpath.pxi	(revision 40156)
+++ src/lxml/xpath.pxi	(working copy)
@@ -143,9 +143,8 @@
     def registerNamespaces(self, namespaces):
         """Register a prefix -> uri dict.
         """
-        add = self._context.addNamespace
         for prefix, uri in namespaces.items():
-            add(prefix, uri)
+            self._context.addNamespace(prefix, uri)
 
     def __call__(self, _path, **_variables):
         """Evaluate an XPath expression on the document.