locale grouping strings should end in '\0'
diff --git a/Objects/stringlib/formatter.h b/Objects/stringlib/formatter.h
index a807b97..5b7b3dc 100644
--- a/Objects/stringlib/formatter.h
+++ b/Objects/stringlib/formatter.h
@@ -649,7 +649,7 @@
case LT_DEFAULT_LOCALE:
locale_info->decimal_point = ".";
locale_info->thousands_sep = ",";
- locale_info->grouping = "\3"; /* Group every 3 characters,
+ locale_info->grouping = "\3\0"; /* Group every 3 characters,
trailing 0 means repeat
infinitely. */
break;