diff --git a/Include/pythonrun.h b/Include/pythonrun.h
index 28e1690..09d3ee5 100644
--- a/Include/pythonrun.h
+++ b/Include/pythonrun.h
@@ -10,7 +10,7 @@
 #define PyCF_MASK (CO_FUTURE_DIVISION | CO_FUTURE_ABSOLUTE_IMPORT | \
                    CO_FUTURE_WITH_STATEMENT | CO_FUTURE_PRINT_FUNCTION | \
                    CO_FUTURE_UNICODE_LITERALS | CO_FUTURE_BARRY_AS_BDFL)
-#define PyCF_MASK_OBSOLETE 0
+#define PyCF_MASK_OBSOLETE (CO_NESTED)
 #define PyCF_SOURCE_IS_UTF8  0x0100
 #define PyCF_DONT_IMPLY_DEDENT 0x0200
 #define PyCF_ONLY_AST 0x0400