diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 29e3393..3d977f4 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -1682,6 +1682,10 @@
 	initerrors();
 	(void) dictinsert(builtin_dict, "None", None);
 	(void) dictinsert(builtin_dict, "Ellipsis", Py_Ellipsis);
+	(void) dictinsert(builtin_dict, "__debug__",
+			  newintobject(Py_OptimizeFlag == 0));
+	if (err_occurred())
+		fatal("error creating None/Ellipsis/__debug__ in __builtin__");
 }