diff --git a/grub-core/script/yylex.l b/grub-core/script/yylex.l
index 9c2cfe115..95b219170 100644
--- a/grub-core/script/yylex.l
+++ b/grub-core/script/yylex.l
@@ -92,7 +92,7 @@ typedef size_t yy_size_t;
 #define stdout 0
 
 #define fprintf(...) 0
-#define exit(...)
+#define exit(...) grub_fatal("fatal error in lexer")
 #endif
 
 }