use NULL for the ends of tables
diff --git a/Modules/_io/stringio.c b/Modules/_io/stringio.c
index d75a604..136f41d 100644
--- a/Modules/_io/stringio.c
+++ b/Modules/_io/stringio.c
@@ -723,7 +723,7 @@
     {"encoding",       (getter)stringio_encoding,       NULL, NULL},
     {"errors",         (getter)stringio_errors,         NULL, NULL},
     {"line_buffering", (getter)stringio_line_buffering, NULL, NULL},
-    {0}
+    {NULL}
 };
 
 PyTypeObject PyStringIO_Type = {