diff --git a/parser/parser_lex.l b/parser/parser_lex.l
index 97c2e849b..97250f958 100644
--- a/parser/parser_lex.l
+++ b/parser/parser_lex.l
@@ -25,6 +25,7 @@
 %option noyy_top_state
 %option nounput
 %option stack
+%option nodefault
 
 %{
 #include <stdio.h>