diff --git a/Packages/vChewing_MainAssembly/Sources/MainAssembly/SessionCtl_Delegates.swift b/Packages/vChewing_MainAssembly/Sources/MainAssembly/SessionCtl_Delegates.swift
index 23b2aaa6..4b690c16 100644
--- a/Packages/vChewing_MainAssembly/Sources/MainAssembly/SessionCtl_Delegates.swift
+++ b/Packages/vChewing_MainAssembly/Sources/MainAssembly/SessionCtl_Delegates.swift
@@ -14,6 +14,7 @@ import Shared
 
 extension SessionCtl: InputHandlerDelegate {
   public var clientMitigationLevel: Int {
+    guard !PrefMgr.shared.securityHardenedCompositionBuffer else { return 2 }
     guard
       let result = PrefMgr.shared.clientsIMKTextInputIncapable[clientBundleIdentifier]
     else {