diff --git a/skeletons/per_support.h b/skeletons/per_support.h
index 420bb83..2708724 100644
--- a/skeletons/per_support.h
+++ b/skeletons/per_support.h
@@ -29,6 +29,8 @@
 typedef struct asn_per_constraints_s {
 	asn_per_constraint_t value;
 	asn_per_constraint_t size;
+	int (*value2code)(unsigned int value);
+	int (*code2value)(unsigned int code);
 } asn_per_constraints_t;
 
 /*