diff --git a/Lib/test/test_signal.py b/Lib/test/test_signal.py
index 50cae0793b5..92747cf109c 100644
--- a/Lib/test/test_signal.py
+++ b/Lib/test/test_signal.py
@@ -473,7 +473,7 @@ class SiginterruptTest(unittest.TestCase):
                 stdout = first_line + stdout
                 exitcode = process.wait()
                 if exitcode not in (2, 3):
-                    raise Exception("Child error (exit code %s): %s"
+                    raise Exception("Child error (exit code %s): %r"
                                     % (exitcode, stdout))
                 return (exitcode == 3)