diff --git a/Lib/test/test_urllib2.py b/Lib/test/test_urllib2.py
index 11848e0..080c2f1 100644
--- a/Lib/test/test_urllib2.py
+++ b/Lib/test/test_urllib2.py
@@ -1220,6 +1220,7 @@
         self.get.add_data("spam")
         self.assertTrue(self.get.has_data())
         self.assertEqual("POST", self.get.get_method())
+        self.assertRaises(TypeError,self.get.add_data, "more spam")
 
     def test_get_full_url(self):
         self.assertEqual("http://www.python.org/~jeremy/",
diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index b9de479..5bdc103 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -192,6 +192,9 @@
     # Begin deprecated methods
 
     def add_data(self, data):
+        if self.has_data():
+            raise TypeError("Request Obj already contains data: %s" %
+                            self.data)
         self.data = data
 
     def has_data(self):