diff --git a/Source/Modules/ControllerModules/InputState.swift b/Source/Modules/ControllerModules/InputState.swift
index 2034030a..a3d8ded7 100644
--- a/Source/Modules/ControllerModules/InputState.swift
+++ b/Source/Modules/ControllerModules/InputState.swift
@@ -194,8 +194,8 @@ class InputState {
         )
       }
 
-      let exactBegin = composingBuffer.utf16CharIndex(from: markedRange.lowerBound)
-      let exactEnd = composingBuffer.utf16CharIndex(from: markedRange.upperBound)
+      let exactBegin = composingBuffer.charIndexLiteral(from: markedRange.lowerBound)
+      let exactEnd = composingBuffer.charIndexLiteral(from: markedRange.upperBound)
       let selectedReadings = readings[exactBegin..<exactEnd]
       let joined = selectedReadings.joined(separator: "-")
       let exist = mgrLangModel.checkIfUserPhraseExist(
@@ -295,8 +295,8 @@ class InputState {
 
     var chkIfUserPhraseExists: Bool {
       let text = composingBuffer.utf16SubString(with: markedRange)
-      let exactBegin = composingBuffer.utf16CharIndex(from: markedRange.lowerBound)
-      let exactEnd = composingBuffer.utf16CharIndex(from: markedRange.upperBound)
+      let exactBegin = composingBuffer.charIndexLiteral(from: markedRange.lowerBound)
+      let exactEnd = composingBuffer.charIndexLiteral(from: markedRange.upperBound)
       let selectedReadings = readings[exactBegin..<exactEnd]
       let joined = selectedReadings.joined(separator: "-")
       return mgrLangModel.checkIfUserPhraseExist(
@@ -306,8 +306,8 @@ class InputState {
 
     var userPhrase: String {
       let text = composingBuffer.utf16SubString(with: markedRange)
-      let exactBegin = composingBuffer.utf16CharIndex(from: markedRange.lowerBound)
-      let exactEnd = composingBuffer.utf16CharIndex(from: markedRange.upperBound)
+      let exactBegin = composingBuffer.charIndexLiteral(from: markedRange.lowerBound)
+      let exactEnd = composingBuffer.charIndexLiteral(from: markedRange.upperBound)
       let selectedReadings = readings[exactBegin..<exactEnd]
       let joined = selectedReadings.joined(separator: "-")
       return "\(text) \(joined)"
@@ -316,8 +316,8 @@ class InputState {
     var userPhraseConverted: String {
       let text =
         OpenCCBridge.crossConvert(composingBuffer.utf16SubString(with: markedRange)) ?? ""
-      let exactBegin = composingBuffer.utf16CharIndex(from: markedRange.lowerBound)
-      let exactEnd = composingBuffer.utf16CharIndex(from: markedRange.upperBound)
+      let exactBegin = composingBuffer.charIndexLiteral(from: markedRange.lowerBound)
+      let exactEnd = composingBuffer.charIndexLiteral(from: markedRange.upperBound)
       let selectedReadings = readings[exactBegin..<exactEnd]
       let joined = selectedReadings.joined(separator: "-")
       let convertedMark = "#𝙊𝙥𝙚𝙣𝘾𝘾"
diff --git a/Source/Modules/ControllerModules/StringUtils.swift b/Source/Modules/ControllerModules/StringUtils.swift
index 25fbe208..d2e33224 100644
--- a/Source/Modules/ControllerModules/StringUtils.swift
+++ b/Source/Modules/ControllerModules/StringUtils.swift
@@ -44,7 +44,7 @@ extension String {
   /// string have different lengths once the string contains such Emoji. The
   /// method helps to find the index in a Swift string by passing the index
   /// in an NSString (or .utf16).
-  public func utf16CharIndex(from utf16Index: Int) -> Int {
+  public func charIndexLiteral(from utf16Index: Int) -> Int {
     var length = 0
     for (i, character) in self.enumerated() {
       length += character.utf16.count
@@ -56,12 +56,12 @@ extension String {
   }
 
   public func utf16NextPosition(for index: Int) -> Int {
-    let fixedIndex = min(utf16CharIndex(from: index) + 1, count)
+    let fixedIndex = min(charIndexLiteral(from: index) + 1, count)
     return self[..<self.index(startIndex, offsetBy: fixedIndex)].utf16.count
   }
 
   public func utf16PreviousPosition(for index: Int) -> Int {
-    let fixedIndex = max(utf16CharIndex(from: index) - 1, 0)
+    let fixedIndex = max(charIndexLiteral(from: index) - 1, 0)
     return self[..<self.index(startIndex, offsetBy: fixedIndex)].utf16.count
   }