diff --git a/Source/Modules/IMEModules/IME.swift b/Source/Modules/IMEModules/IME.swift
index 0704414a..df50d1b3 100644
--- a/Source/Modules/IMEModules/IME.swift
+++ b/Source/Modules/IMEModules/IME.swift
@@ -364,7 +364,7 @@ extension String: LocalizedError {
   }
 }
 
-// MARK: - Ensuring trailing slash of a string:
+// MARK: - Ensuring trailing slash of a string
 
 extension String {
   mutating func ensureTrailingSlash() {
@@ -373,3 +373,16 @@ extension String {
     }
   }
 }
+
+// MARK: - CharCode printability check
+
+// Ref: https://forums.swift.org/t/57085/5
+extension UniChar {
+  public func isPrintable() -> Bool {
+    guard Unicode.Scalar(UInt32(self)) != nil else {
+      struct NotAWholeScalar: Error {}
+      return false
+    }
+    return true
+  }
+}