diff --git a/Source/Modules/ControllerModules/KeyHandler_States.swift b/Source/Modules/ControllerModules/KeyHandler_States.swift
index 13e49af1..b84fad5a 100644
--- a/Source/Modules/ControllerModules/KeyHandler_States.swift
+++ b/Source/Modules/ControllerModules/KeyHandler_States.swift
@@ -116,7 +116,7 @@ extension KeyHandler {
     var cleanedComposition = ""
     for theChar in composedText {
       if let charCode = theChar.utf16.first {
-        if !(theChar.isASCII && !(charCode.isPrintable())) {
+        if !(theChar.isASCII && !(charCode.isPrintable)) {
           cleanedComposition += String(theChar)
         }
       }
diff --git a/Source/Modules/ControllerModules/ctlInputMethod_Core.swift b/Source/Modules/ControllerModules/ctlInputMethod_Core.swift
index b35ea3c1..017a4320 100644
--- a/Source/Modules/ControllerModules/ctlInputMethod_Core.swift
+++ b/Source/Modules/ControllerModules/ctlInputMethod_Core.swift
@@ -210,7 +210,7 @@ class ctlInputMethod: IMKInputController {
 
     // 無法列印的訊號輸入，一概不作處理。
     // 這個過程不能放在 KeyHandler 內，否則不會起作用。
-    if !input.charCode.isPrintable() {
+    if !input.charCode.isPrintable {
       return false
     }
 
diff --git a/Source/Modules/IMEModules/IME.swift b/Source/Modules/IMEModules/IME.swift
index 7ae55cd5..e79a040d 100644
--- a/Source/Modules/IMEModules/IME.swift
+++ b/Source/Modules/IMEModules/IME.swift
@@ -413,7 +413,7 @@ extension String {
 
 // Ref: https://forums.swift.org/t/57085/5
 extension UniChar {
-  public func isPrintable() -> Bool {
+  public var isPrintable: Bool {
     guard Unicode.Scalar(UInt32(self)) != nil else {
       struct NotAWholeScalar: Error {}
       return false