diff --git a/Tokenizer.cs b/Tokenizer.cs
index 6c5f76f..f8e97d8 100644
--- a/Tokenizer.cs
+++ b/Tokenizer.cs
@@ -701,7 +701,7 @@ class Tokenizer
 			break;
 			case State.Zero:
 			{
-				if(ch == 'x')
+				if(ch is 'x' or 'X')
 				{
 					currentToken!.type = null;
 					state = State.HexNumberX;