diff --git a/lib/hx509/sel.h b/lib/hx509/sel.h
index 177ec0a65b..52a84d31c5 100644
--- a/lib/hx509/sel.h
+++ b/lib/hx509/sel.h
@@ -67,14 +67,18 @@ struct hx_expr_input {
 
 extern struct hx_expr_input _hx509_expr_input;
 
-#define yyparse _hx509_sel_yyparse
+#if !defined(yylex)
 #define yylex   _hx509_sel_yylex
+#define yywrap  _hx509_sel_yywrap
+#endif
+#if !defined(yyparse)
+#define yyparse _hx509_sel_yyparse
 #define yyerror _hx509_sel_yyerror
 #define yylval  _hx509_sel_yylval
 #define yychar  _hx509_sel_yychar
 #define yydebug _hx509_sel_yydebug
 #define yynerrs _hx509_sel_yynerrs
-#define yywrap  _hx509_sel_yywrap
+#endif
 
 int  _hx509_sel_yyparse(void);
 int  _hx509_sel_yylex(void);