diff --git a/operational b/operational
index 5c6908446ee8d5aba26d38294bcfb3778b6d226f..945cb84af43e23caafa5490e357a7eff44047ab3 100644
--- a/operational
+++ b/operational
@@ -136,8 +136,12 @@ see ~/c/gtk-im-module/, it uses myastyle-pre-commit-check in git pre-commit
 - problems
   - can I make this change backward compatible?
 
-    TODO what will happen when zero asks dbus to set FuzzyFlag property, if
+    DONE what will happen when zero asks dbus to set FuzzyFlag property, if
     running an old zero-pinyin-service?
+
+    dbus-set-property returns nil if the property doesn't exist.
+    I will show a warning.
+
   - property generated code is okay.
   - how to access that property in zero-pinyin-service.c?
     guint zero_pinyin_service_get_fuzzy_flag (ZeroPinyinService *object);