diff --git a/Source/Modules/IMEModules/IME.swift b/Source/Modules/IMEModules/IME.swift
index 21002a70..ca108ca4 100644
--- a/Source/Modules/IMEModules/IME.swift
+++ b/Source/Modules/IMEModules/IME.swift
@@ -373,7 +373,7 @@ public enum IME {
 // Extend the RangeReplaceableCollection to allow it clean duplicated characters.
 // Ref: https://stackoverflow.com/questions/25738817/
 extension RangeReplaceableCollection where Element: Hashable {
-  var charDeDuplicate: Self {
+  var deduplicate: Self {
     var set = Set<Element>()
     return filter { set.insert($0).inserted }
   }
diff --git a/Source/UI/PrefUI/suiPrefPaneExperience.swift b/Source/UI/PrefUI/suiPrefPaneExperience.swift
index e288d504..e6273f1c 100644
--- a/Source/UI/PrefUI/suiPrefPaneExperience.swift
+++ b/Source/UI/PrefUI/suiPrefPaneExperience.swift
@@ -65,7 +65,7 @@ struct suiPrefPaneExperience: View {
         ComboBox(items: mgrPrefs.suggestedCandidateKeys, text: $selSelectionKeys).frame(width: 180).onChange(
           of: selSelectionKeys
         ) { value in
-          let keys: String = (value.trimmingCharacters(in: .whitespacesAndNewlines) as String).charDeDuplicate
+          let keys: String = value.trimmingCharacters(in: .whitespacesAndNewlines).deduplicate
           do {
             try mgrPrefs.validate(candidateKeys: keys)
             mgrPrefs.candidateKeys = keys
diff --git a/Source/WindowControllers/ctlPrefWindow.swift b/Source/WindowControllers/ctlPrefWindow.swift
index b73f64ff..d7de5183 100644
--- a/Source/WindowControllers/ctlPrefWindow.swift
+++ b/Source/WindowControllers/ctlPrefWindow.swift
@@ -228,7 +228,7 @@ class ctlPrefWindow: NSWindowController {
       let keys = (sender as AnyObject).stringValue?.trimmingCharacters(
         in: .whitespacesAndNewlines
       )
-      .charDeDuplicate
+      .deduplicate
     else {
       return
     }