diff --git a/Tokenizer.cs b/Tokenizer.cs
index 4ebf43d..562bf91 100644
--- a/Tokenizer.cs
+++ b/Tokenizer.cs
@@ -493,13 +493,13 @@ class Tokenizer
 					case 'x':
 					{
 						state = State.QuoteBackslashX;
+						throw new NotImplementedException($"\\u escape sequences are broken right now");
 					}
-					break;
 					case 'u':
 					{
 						state = State.QuoteBackslashU;
+						throw new NotImplementedException($"\\u escape sequences are broken right now");
 					}
-					break;
 					default: throw new Exception($"Unknown escape sequence: \\{ch} at {currentLocation}");
 				}
 			}