diff --git a/Lib/string.py b/Lib/string.py
index ad2146c..f60753f 100644
--- a/Lib/string.py
+++ b/Lib/string.py
@@ -208,7 +208,7 @@
         return self.vformat(format_string, args, kwargs)
 
     def vformat(self, format_string, args, kwargs):
-        used_args = self.get_empty_used_args()
+        used_args = set()
         result = []
         for literal_text, field_name, format_spec, conversion in \
                 self.parse(format_string):
@@ -223,7 +223,9 @@
                 #  the formatting
 
                 # given the field_name, find the object it references
-                obj = self.get_field(field_name, args, kwargs, used_args)
+                #  and the argument it came from
+                obj, arg_used = self.get_field(field_name, args, kwargs, used_args)
+                used_args.add(arg_used)
 
                 # do any conversion on the resulting object
                 obj = self.convert_field(obj, conversion)
@@ -235,10 +237,6 @@
         return ''.join(result)
 
 
-    def get_empty_used_args(self):
-        return set()
-
-
     def get_value(self, key, args, kwargs):
         if isinstance(key, int):
             return args[key]
@@ -296,4 +294,4 @@
             else:
                 obj = obj[i]
 
-        return obj
+        return obj, first