          (dav_namespace, "alternate-URI-set"),
          (dav_namespace, "principal-URL"    ),
          (dav_namespace, "group-member-set" ),
-@@ -1585,14 +1929,11 @@
+@@ -1585,14 +1930,11 @@
      )
  
      def davComplianceClasses(self):

             "Not a meta-principal: %r" % (principal,)
         )
 
@@ -1517,6 +1601,270 @@
         return None
 
     ##

 
         if isinstance(principal, davxml.HRef):
             yield principal
+            return
         else:
             yield None
 
