diff --git a/tests/mypy_test.py b/tests/mypy_test.py
index cb042d83f..aebf1999a 100755
--- a/tests/mypy_test.py
+++ b/tests/mypy_test.py
@@ -132,6 +132,7 @@ def main():
             flags = ['--python-version', '%d.%d' % (major, minor)]
             flags.append('--strict-optional')
             flags.append('--no-site-packages')
+            flags.append('--show-traceback')
             if args.no_implicit_optional:
                 flags.append('--no-implicit-optional')
             if args.warn_unused_ignores: