diff --git a/Packages/vChewing_Shared/Sources/Shared/Protocols/PrefMgrProtocol.swift b/Packages/vChewing_Shared/Sources/Shared/Protocols/PrefMgrProtocol.swift
index 62411a16..a4409c25 100644
--- a/Packages/vChewing_Shared/Sources/Shared/Protocols/PrefMgrProtocol.swift
+++ b/Packages/vChewing_Shared/Sources/Shared/Protocols/PrefMgrProtocol.swift
@@ -11,6 +11,7 @@ import Foundation
 public protocol PrefMgrProtocol {
   var isDebugModeEnabled: Bool { get set }
   var failureFlagForUOMObservation: Bool { get set }
+  var failureFlagForIMKCandidates: Bool { get set }
   var deltaOfCalendarYears: Int { get set }
   var mostRecentInputMode: String { get set }
   var useExternalFactoryDict: Bool { get set }
diff --git a/Packages/vChewing_Shared/Sources/Shared/Shared.swift b/Packages/vChewing_Shared/Sources/Shared/Shared.swift
index d1736d1a..53a66fda 100644
--- a/Packages/vChewing_Shared/Sources/Shared/Shared.swift
+++ b/Packages/vChewing_Shared/Sources/Shared/Shared.swift
@@ -14,6 +14,7 @@ import SwiftExtension
 public enum UserDef: String, CaseIterable {
   case kIsDebugModeEnabled = "_DebugMode"
   case kFailureFlagForUOMObservation = "_FailureFlag_UOMObservation"
+  case kFailureFlagForIMKCandidates = "_FailureFlag_IMKCandidates"
   case kDeltaOfCalendarYears = "DeltaOfCalendarYears"
   case kMostRecentInputMode = "MostRecentInputMode"
   case kCassettePath = "CassettePath"
diff --git a/Source/Modules/PrefMgr_Core.swift b/Source/Modules/PrefMgr_Core.swift
index 46be5f1e..173fc2d8 100644
--- a/Source/Modules/PrefMgr_Core.swift
+++ b/Source/Modules/PrefMgr_Core.swift
@@ -34,6 +34,9 @@ public class PrefMgr: PrefMgrProtocol {
   @AppProperty(key: UserDef.kFailureFlagForUOMObservation.rawValue, defaultValue: false)
   public var failureFlagForUOMObservation: Bool
 
+  @AppProperty(key: UserDef.kFailureFlagForIMKCandidates.rawValue, defaultValue: false)
+  public var failureFlagForIMKCandidates: Bool
+
   @AppProperty(key: UserDef.kDeltaOfCalendarYears.rawValue, defaultValue: -2000)
   public var deltaOfCalendarYears: Int