diff --git a/scanner/lexer.go b/scanner/lexer.go
index dd6c05a..706e371 100644
--- a/scanner/lexer.go
+++ b/scanner/lexer.go
@@ -54,8 +54,10 @@ func Rune2Class(r rune) int {
 	if unicode.IsGraphic(r) {
 		return classUnicodeGraphic
 	}
-	// return classOther
-	return -1
+	if r == lex.RuneEOF {
+		return int(r)
+	}
+	return classOther
 }
 
 // NewLexer the Lexer constructor