diff --git a/Lib/test/pickletester.py b/Lib/test/pickletester.py
index 057cb5e..927939e 100644
--- a/Lib/test/pickletester.py
+++ b/Lib/test/pickletester.py
@@ -936,7 +936,7 @@
 
     def test_dump_closed_file(self):
         import os
-        f = open(TESTFN, "w")
+        f = open(TESTFN, "wb")
         try:
             f.close()
             self.assertRaises(ValueError, self.module.dump, 123, f)
@@ -945,7 +945,7 @@
 
     def test_load_closed_file(self):
         import os
-        f = open(TESTFN, "w")
+        f = open(TESTFN, "wb")
         try:
             f.close()
             self.assertRaises(ValueError, self.module.dump, 123, f)