diff --git a/ArchiSteamFarm/Bot.cs b/ArchiSteamFarm/Bot.cs
index 61b050e85..e1f7d1dab 100755
--- a/ArchiSteamFarm/Bot.cs
+++ b/ArchiSteamFarm/Bot.cs
@@ -541,7 +541,7 @@ namespace ArchiSteamFarm {
 
 					break;
 				case ASF.EUserInputType.TwoFactorAuthentication:
-					if (((inputValue.Length != MobileAuthenticator.CodeDigits) && (inputValue.Length != MobileAuthenticator.BackupCodeDigits)) || inputValue.Any(character => !MobileAuthenticator.CodeCharacters.Contains(character))) {
+					if (((inputValue.Length != MobileAuthenticator.CodeDigits) && (inputValue.Length != MobileAuthenticator.BackupCodeDigits)) || inputValue.Any(character => !MobileAuthenticator.CodeCharacters.Contains(char.ToUpperInvariant(character)))) {
 						return false;
 					}