diff --git a/lib/hx509/sel-gram.y b/lib/hx509/sel-gram.y
index 09f641d7c..5d985298d 100644
--- a/lib/hx509/sel-gram.y
+++ b/lib/hx509/sel-gram.y
@@ -78,6 +78,9 @@
 %token <string> STRING
 %token <string> IDENTIFIER
 
+%destructor { _hx509_expr_free($$); } expr comp word words number string function variable variables
+%destructor { free($$); } NUMBER STRING IDENTIFIER
+
 %left '!'
 %left kw_AND
 %left kw_OR