diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index 196d18c..7eef4c0 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -598,8 +598,12 @@
         fileobj = os.fdopen(fd, "w+b")
         try:
             writer = csv.DictWriter(fileobj, fieldnames = ["f1", "f2", "f3"])
+            writer.writeheader()
+            fileobj.seek(0)
+            self.assertEqual(fileobj.readline(), "f1,f2,f3\r\n")
             writer.writerow({"f1": 10, "f3": "abc"})
             fileobj.seek(0)
+            fileobj.readline() # header
             self.assertEqual(fileobj.read(), "10,,abc\r\n")
         finally:
             fileobj.close()