diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 952f7e5..af960bc 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1231,7 +1231,7 @@
 	PyModuleDef_HEAD_INIT,
 	"sys",
 	sys_doc,
-	0,
+	-1, /* multiple "initialization" just copies the module dict. */
 	sys_methods,
 	NULL,
 	NULL,