diff --git a/Lib/test/test_tools.py b/Lib/test/test_tools.py
index 9403da7..006220a 100644
--- a/Lib/test/test_tools.py
+++ b/Lib/test/test_tools.py
@@ -50,7 +50,7 @@
                 (sys.executable, self.script) + args,
                 stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                 universal_newlines=True) as proc:
-            out, err = proc.communicate(source.encode())
+            out, err = proc.communicate(source)
         self.assertIsNone(err)
         return out