diff --git a/Include/pydebug.h b/Include/pydebug.h
index cd56196..0a31f5b 100644
--- a/Include/pydebug.h
+++ b/Include/pydebug.h
@@ -18,6 +18,7 @@
 PyAPI_DATA(int) Py_DivisionWarningFlag;
 PyAPI_DATA(int) Py_DontWriteBytecodeFlag;
 PyAPI_DATA(int) Py_NoUserSiteDirectory;
+PyAPI_DATA(int) Py_UnbufferedStdioFlag;
 
 /* this is a wrapper around getenv() that pays attention to
    Py_IgnoreEnvironmentFlag.  It should be used for getting variables like