diff --git a/Include/pydebug.h b/Include/pydebug.h
index 03eae8e..f187bed 100644
--- a/Include/pydebug.h
+++ b/Include/pydebug.h
@@ -39,6 +39,7 @@
 extern DL_IMPORT(int) Py_VerboseFlag;
 extern DL_IMPORT(int) Py_SuppressPrintingFlag;
 extern DL_IMPORT(int) Py_InteractiveFlag;
+extern DL_IMPORT(int) Py_OptimizeFlag;
 
 void Py_FatalError	Py_PROTO((char *));