diff --git a/Lib/ConfigParser.py b/Lib/ConfigParser.py
index 65c6ae2..b6af6f9 100644
--- a/Lib/ConfigParser.py
+++ b/Lib/ConfigParser.py
@@ -588,7 +588,7 @@
                     value = value % vars
                 except KeyError, e:
                     raise InterpolationMissingOptionError(
-                        option, section, rawval, e[0])
+                        option, section, rawval, e.args[0])
             else:
                 break
         if "%(" in value: