diff --git a/include/ntapi/nt_object.h b/include/ntapi/nt_object.h
index bc4df6f..1a34a40 100644
--- a/include/ntapi/nt_object.h
+++ b/include/ntapi/nt_object.h
@@ -393,7 +393,7 @@ typedef struct _nt_keyed_object_directory_name {
 } nt_keyed_object_directory_name, nt_keyed_objdir_name;
 
 
-typedef void nt_io_apc_routine(
+typedef void __stdcall nt_io_apc_routine(
 	void *			apc_context,
 	nt_io_status_block *	io_status_block,
 	uint32_t		reserved);