diff --git a/Packages/vChewing_Shared/Sources/Shared/Protocols/PrefMgrProtocol.swift b/Packages/vChewing_Shared/Sources/Shared/Protocols/PrefMgrProtocol.swift
index f198e9d8..94bf4e02 100644
--- a/Packages/vChewing_Shared/Sources/Shared/Protocols/PrefMgrProtocol.swift
+++ b/Packages/vChewing_Shared/Sources/Shared/Protocols/PrefMgrProtocol.swift
@@ -45,6 +45,7 @@ public protocol PrefMgrProtocol {
   var onlyLoadFactoryLangModelsIfNeeded: Bool { get set }
   var useIMKCandidateWindow: Bool { get set }
   var handleDefaultCandidateFontsByLangIdentifier: Bool { get set }
+  var disableSegmentedThickUnderlineInMarkingModeForManagedClients: Bool { get set }
   var maxCandidateLength: Int { get set }
   var shouldNotFartInLieuOfBeep: Bool { get set }
   var showHanyuPinyinInCompositionBuffer: Bool { get set }
diff --git a/Packages/vChewing_Shared/Sources/Shared/Shared.swift b/Packages/vChewing_Shared/Sources/Shared/Shared.swift
index ada1b14e..15c0bf75 100644
--- a/Packages/vChewing_Shared/Sources/Shared/Shared.swift
+++ b/Packages/vChewing_Shared/Sources/Shared/Shared.swift
@@ -73,6 +73,8 @@ public enum UserDef: String, CaseIterable {
 
   case kUseIMKCandidateWindow = "UseIMKCandidateWindow"
   case kHandleDefaultCandidateFontsByLangIdentifier = "HandleDefaultCandidateFontsByLangIdentifier"
+  case kDisableSegmentedThickUnderlineInMarkingModeForManagedClients
+    = "DisableSegmentedThickUnderlineInMarkingModeForManagedClients"
 
   case kCandidateTextFontName = "CandidateTextFontName"
   case kCandidateKeys = "CandidateKeys"
diff --git a/Source/Modules/PrefMgr_Core.swift b/Source/Modules/PrefMgr_Core.swift
index f3334541..d3f284a7 100644
--- a/Source/Modules/PrefMgr_Core.swift
+++ b/Source/Modules/PrefMgr_Core.swift
@@ -182,6 +182,12 @@ public class PrefMgr: PrefMgrProtocol {
   @AppProperty(key: UserDef.kHandleDefaultCandidateFontsByLangIdentifier.rawValue, defaultValue: false)
   public var handleDefaultCandidateFontsByLangIdentifier: Bool
 
+  @AppProperty(
+    key: UserDef.kDisableSegmentedThickUnderlineInMarkingModeForManagedClients.rawValue,
+    defaultValue: false
+  )
+  public var disableSegmentedThickUnderlineInMarkingModeForManagedClients: Bool
+
   // MARK: - Settings (Tier 3)
 
   @AppProperty(key: UserDef.kMaxCandidateLength.rawValue, defaultValue: 10)