diff --git a/sources/SquirrelInputController.swift b/sources/SquirrelInputController.swift
index 05d2c63e4..6d5928bf8 100644
--- a/sources/SquirrelInputController.swift
+++ b/sources/SquirrelInputController.swift
@@ -97,7 +97,7 @@ final class SquirrelInputController: IMKInputController {
 
       let keyCode = event.keyCode
       var keyChars = event.charactersIgnoringModifiers
-      if let code = keyChars?.first, !code.isLetter {
+      if let code = keyChars?.first, !code.isASCII {
         keyChars = event.characters
       }
       // print("[DEBUG] KEYDOWN client: \(sender ?? "nil"), modifiers: \(modifiers), keyCode: \(keyCode), keyChars: [\(keyChars ?? "empty")]")