diff --git a/Lib/test/test_tools.py b/Lib/test/test_tools.py
index 4756e4f..f60b4c7 100644
--- a/Lib/test/test_tools.py
+++ b/Lib/test/test_tools.py
@@ -57,6 +57,7 @@
         return '\n'.join(line.lstrip() for line in data.splitlines()) + '\n'
 
     def test_selftest(self):
+        self.maxDiff = None
         with temp_dir() as directory:
             data_path = os.path.join(directory, '_test.py')
             with open(self.script) as f: