diff --git a/reactos/include/ndk/obfuncs.h b/reactos/include/ndk/obfuncs.h
index a9b54d32c8b..96cc917564f 100644
--- a/reactos/include/ndk/obfuncs.h
+++ b/reactos/include/ndk/obfuncs.h
@@ -105,7 +105,7 @@ ObOpenObjectByName(
     _In_ POBJECT_ATTRIBUTES ObjectAttributes,
     _In_ POBJECT_TYPE ObjectType,
     _In_ KPROCESSOR_MODE AccessMode,
-    _In_ PACCESS_STATE PassedAccessState,
+    _In_opt_ PACCESS_STATE PassedAccessState,
     _In_ ACCESS_MASK DesiredAccess,
     _Inout_ PVOID ParseContext,
     _Out_ PHANDLE Handle