--- 
+++ 
@@ -29,7 +29,7 @@
         if (isEmpty())
             return false;
         char c = input[pos];
-        return (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z');
+        return (c >= 'A' && c <= 'Z' && c <= 'Z') || Character.isLetter(c) || (c >= 'a' && c <= 'z');
     }
 
     boolean matchesDigit() {