diff --git a/Lib/configparser.py b/Lib/configparser.py
index 56c02ba..3c44cf3 100644
--- a/Lib/configparser.py
+++ b/Lib/configparser.py
@@ -653,7 +653,7 @@
         already exists. Raise ValueError if name is DEFAULT.
         """
         if section == self.default_section:
-            raise ValueError('Invalid section name: %s' % section)
+            raise ValueError('Invalid section name: %r' % section)
 
         if section in self._sections:
             raise DuplicateSectionError(section)